8 files changed, 1846 insertions, 0 deletions
diff --git a/2021/day3/Cargo.toml b/2021/day3/Cargo.toml
new file mode 100644
index 0000000..898e70d
--- /dev/null
+++ b/2021/day3/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "day3"
+version = "0.1.0"
+edition = "2021"
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[dependencies]
diff --git a/2021/day3/input b/2021/day3/input
new file mode 100644
index 0000000..929c455
--- /dev/null
+++ b/2021/day3/input
@@ -0,0 +1,1000 @@
+010101110000
+010011000110
+010101000011
+111100100001
+011100110101
+110001010101
+001111110101
+101100011100
+010111111011
+101010111101
+101000001110
+001000100001
+000100011110
+100011000100
+101100100001
+101010111010
+111000001011
+101101001011
+000010010110
+110111100111
+111101011110
+100100010010
+110001011110
+010011101000
+111110000110
+110001011111
+001001010110
+110111100100
+100111000101
+110011110000
+000110000010
+010001100001
+111110111011
+100010101011
+000000010101
+100010101110
+100110100111
+100111101111
+110011110001
+001000111100
+001101010010
+111101011101
+011000110001
+111111011010
+011000000000
+100000111001
+011110101100
+011101010111
+011001111110
+011100101101
+101100010011
+001100110000
+110101101100
+110110001100
+000101101110
+001010110010
+111110110110
+111010010011
+100010111111
+001001001000
+110111001011
+010110000010
+100000000100
+100001010010
+110010011101
+000001011011
+000100010100
+101011000001
+011101110111
+001100010100
+101000010110
+111111001100
+110011001011
+110000000000
+010100110101
+001111100011
+100011010010
+100111100011
+110101001010
+011111011000
+001010100110
+010101010100
+110111011111
+001001010000
+001011010101
+101111011011
+101001101000
+000011101110
+000101110010
+100011001010
+011001010010
+100100110011
+010010011100
+001100100110
+100111110111
+000111111000
+100000001101
+001111010101
+000001001111
+000101100000
+000101001111
+101010001001
+111011110001
+000111100011
+110011000010
+110011111101
+101001010110
+101111111000
+000110100010
+101111010001
+010011110001
+111110010010
+101111011101
+101110111101
+010001011111
+101110011010
+001110001100
+000110011001
+000101000101
+101010111011
+110010101100
+000100101101
+010111011111
+111001010110
+000010100100
+100000111100
+101101110001
+100001111010
+000111010010
+111100000110
+010010000000
+010001001011
+111101010000
+010011111110
+111011101011
+110110100110
+100001000011
+010010000110
+010000000001
+000001000101
+011010100000
+001011011000
+110101010001
+011000111110
+010011101101
+010011000011
+011010011101
+001101110100
+010001100101
+111011100011
+010111101000
+111100000010
+010000110000
+000100111001
+010010110100
+000101110110
+000011001110
+111010111100
+100101010001
+111011000101
+011111101100
+000110010001
+100011101111
+100101001110
+101101110010
+000000011010
+000001101000
+010110011000
+110100001001
+111111101100
+011010110001
+011100111101
+001101010110
+100111000111
+000000001111
+001110101010
+101000011001
+000111010111
+100110110001
+100011000011
+110111101011
+000110111001
+000010010011
+010111011001
+000111001000
+100011011010
+011101000100
+101010010100
+010111110000
+011011100111
+000001110001
+000100111000
+111100001011
+100101010000
+000110110100
+110011110111
+111000010111
+101110011000
+110011010000
+001111000100
+111010001001
+110001111000
+011101011111
+000001001100
+110100111011
+110001011011
+001010000100
+110011101110
+101100100100
+100101100001
+001010001010
+101010001000
+000110101001
+001100010000
+110001000101
+000100111110
+000110100111
+100010001010
+100100010110
+010001110011
+101111010010
+100000001001
+000110110000
+100010011011
+111101000001
+101111111011
+111111100110
+101001101010
+000011111011
+110000000011
+000001111010
+001001000100
+101110001101
+100111011111
+110101101110
+100011011011
+101000010001
+101001111000
+111101110010
+000101000011
+100100010100
+010101111101
+100110001011
+010011010111
+110111100101
+110010010101
+100010101101
+100110000110
+001101000001
+111001001000
+010111010011
+000110001111
+010101011010
+000000001000
+001001100100
+101111111001
+001110101000
+000110100100
+001111101111
+010100011000
+010000110110
+011101101110
+010100100100
+111110010101
+101100000110
+011010110000
+001001011101
+000000000101
+100101111001
+110101110110
+100111101010
+010010101101
+010100001111
+111111111110
+011111000000
+000001101111
+011001011001
+001101101000
+011010110110
+100101000110
+110001101110
+110100101011
+010001110100
+011110110101
+010001010001
+110110101000
+010000100011
+010101011001
+101111111010
+000011110010
+001000011101
+110001100010
+110110000011
+010000111011
+111010010000
+011001001000
+000111011010
+011111111100
+111001111100
+001101000100
+101110001011
+101110000111
+011010111111
+110011100111
+001101110010
+011111101111
+001110000110
+010111100001
+110100101001
+101010110010
+111011010100
+101001110010
+101101000100
+100111010001
+000011010110
+100110000100
+101000101010
+000000001010
+110100111010
+110010011010
+100110010100
+011101110010
+000111111010
+001000101001
+110100110010
+100100111011
+011001010111
+111000101010
+011001011011
+011010000000
+001101101110
+101010111000
+101010011000
+011000010101
+111001011010
+100111111111
+001101001100
+111011011010
+110110100011
+111010010100
+000110011101
+011100010011
+011111100111
+010110100000
+001100001000
+000110000110
+000101011011
+101011101011
+111101111110
+111111110000
+101101001100
+011000110110
+100111001000
+011011111100
+001111011110
+111011100100
+000101010010
+100011011000
+100000100110
+100000110011
+011000010110
+001010110100
+100111100010
+011110101011
+110111111010
+011100110110
+100100000000
+011010101101
+001101000010
+010110010111
+100010011100
+111101010101
+011011010111
+000000000110
+101001100000
+010100110011
+010101111111
+101110111001
+101101111000
+101110101000
+011011111110
+010001101010
+001000101010
+111100111111
+001011011110
+101010101001
+011111001010
+001001001111
+101000101101
+001111011000
+000100001101
+101101011000
+001100000100
+001000111101
+000001110100
+111101011111
+111010000010
+101111011111
+001100110101
+101010110001
+001110111010
+010010111110
+101101010011
+100001100110
+110010010001
+111100111001
+000100010001
+110010101010
+111010110101
+000001010110
+000111110110
+111010101100
+011110001100
+010110001001
+010111100011
+001010111000
+100111100111
+110110011001
+010100000000
+001011001111
+110010110000
+100011001111
+100111111011
+110001001001
+000100101111
+011010011011
+001001111101
+111110001100
+101111110010
+101100101110
+100110111001
+111010110011
+110010011110
+001111001101
+010011100111
+000111000011
+101101000000
+000001100101
+011101111001
+110100100110
+000110000001
+110111011101
+011100000110
+001011110100
+010001011011
+110000011110
+110001001011
+110100000001
+011010010100
+010010000101
+001010110111
+110001001111
+101100000001
+010000000000
+101110010001
+001100101110
+010000011010
+010100101011
+011010101100
+111101011011
+110111010000
+111111101111
+111011111011
+110001110111
+011100100011
+100001110101
+100111011001
+100110010000
+100110101110
+110101100001
+001010001101
+011101101000
+110001001110
+110010111011
+111100110100
+101011100011
+010100100101
+010001101111
+111000110101
+001000101011
+101101000101
+011000100111
+001111000011
+011000000011
+000011001111
+001010011111
+101001100010
+101010100001
+001001110010
+101010000111
+010111011010
+110101110111
+000110101111
+000110010011
+010110110010
+100111001011
+001100111111
+111110000001
+110110111000
+101010000100
+011100101010
+001000010101
+010010011001
+011111000110
+010011010011
+001011101101
+001001110100
+110101011100
+011000110100
+010101101000
+100000100000
+011011111010
+011010011111
+111011011101
+001111101110
+001000110101
+010001011100
+110101100010
+001100100100
+001100101011
+100110111000
+001100101101
+101000001011
+001100010101
+001100011010
+101011010101
+110101011111
+101111001011
+000010001111
+011110001111
+110000000100
+000110100001
+010010101111
+110000000110
+010011000000
+011001000101
+001101011010
+000011001101
+110100101010
+111001010111
+010011010101
+111010100101
+111110110101
+111110011100
+110010000110
+000110100011
+001000111000
+000101101100
+101110001010
+010010010110
+100001110111
+111010100010
+110110010111
+101000011000
+100100111010
+001000011011
+111101101011
+101001010111
+100110000011
+100001010001
+011011000001
+010110010101
+110001010000
+001110000000
+111001001110
+011011101100
+000100001111
+111000110011
+111101101101
+100110000000
+100011110110
+001000000010
+110011011000
+111000100110
+100110110000
+010011101010
+111011001010
+001101111000
+001100000111
+001110011110
+100001000100
+000010000111
+011010101001
+111110001001
+110110000010
+011011101101
+110001111010
+011001101110
+010011000010
+100101110100
+101000100001
+000111011101
+101100001011
+100000011010
+111001001001
+100000000001
+000101111001
+100101101101
+111001101111
+001011011011
+000010101000
+001010111010
+000100100011
+001110101101
+100000111000
+110110001110
+000111101101
+001010001111
+011000111011
+100000100100
+100011010110
+000010000000
+001000001101
+010001001110
+000111111011
+100110000001
+110010111000
+111100111100
+001000001100
+000010110100
+011010001110
+110001110101
+001100000101
+100010110100
+111000000010
+110100100101
+010010111011
+010110011001
+001001101100
+001010101010
+100001011100
+010001101001
+000000010010
+000101111010
+011000101011
+111111010101
+011110101111
+011110011001
+001101101101
+111110101110
+101111110100
+010101001111
+010010011101
+000110101100
+011100000011
+100011101001
+101101100111
+110011101100
+000110111010
+000011001000
+111101010011
+011011101110
+111101001100
+100100101111
+111010110111
+000001100110
+110100110101
+110100001011
+111010000001
+001011110011
+001010110101
+100001100000
+101000101100
+011011100001
+000011011011
+100101110001
+101100111100
+010000111110
+010100101101
+001111011111
+110101010000
+000110010100
+001001011011
+110111111011
+111100010110
+110000101011
+111001000100
+000100000111
+001011001110
+011110100010
+011011110101
+001100011001
+111010011111
+011011110110
+111101000000
+101111110000
+011100111000
+010010011011
+101000110010
+001101101111
+010001000011
+001010010110
+101000010010
+110111001111
+011111010101
+111111011001
+100011110011
+110001100100
+100000010100
+001111011010
+111001111000
+110101001011
+101000110001
+111001111111
+110000010111
+000000100100
+101011101110
+111001110111
+001110011010
+110011101000
+001011100100
+011001011111
+010100010101
+011111111010
+010010110000
+100011101110
+000011000110
+001001010111
+010111110100
+010110110101
+010000101000
+101010101010
+000100100010
+000110011000
+101010110101
+100000100001
+101100010010
+010110000110
+011011010011
+000001010010
+011101111110
+100010000100
+000100101110
+010110010001
+101100011011
+010111010000
+101100011111
+010011001010
+100010100000
+001001101001
+110010011001
+111000110100
+111111010000
+111100101110
+101010001010
+111111100100
+011110001110
+101100001111
+001010001100
+110100100011
+011100010101
+110001011000
+000010100001
+011000011110
+000000101101
+000011101101
+111010011000
+000101110100
+111100011010
+101100010110
+100001101011
+110100110100
+101100111010
+010000011110
+101001100011
+000101110001
+001101111111
+111101000101
+100101111101
+001101011110
+011111101011
+100000010101
+011010000001
+011000011101
+110101011110
+111010101000
+110111111100
+101111110011
+101101001001
+000111101001
+010110000011
+110011000000
+000001111101
+001011101000
+001001111011
+110110000111
+101100010101
+101100100111
+000010110001
+110000111011
+110111001000
+010010111111
+100010110000
+010000111100
+101001000111
+010100001100
+001111001010
+010100101010
+100001000010
+010011101111
+100011000001
+110000001101
+011001011110
+100111111001
+001100111101
+010110100110
+001000011001
+101000111110
+000100001011
+111110100111
+011100111001
+100011111001
+100001100001
+110110001011
+110011101111
+011010111011
+110101010110
+010111101001
+111110000011
+111100000111
+011111100100
+101001000001
+110111010100
+000011000000
+000100111101
+001100010011
+100000010011
+010010001001
+010111000100
+110110010100
+011100101110
+110110100010
+100111010111
+001111010011
+000110110110
+000010000110
+110100010001
+010100111101
+011001000110
+101011010100
+001110001101
+101111110101
+110011001010
+110100011100
+001101011000
+100101101110
+000001000111
+111001101011
+101011000010
+001001011111
+111000111010
+111011100110
+001001011100
+000010011000
+000101001001
+100110001111
+010100100010
+001101000101
+010111111100
+100010000001
+110101101111
+100010101010
+110110010001
+011101000111
+011110001010
+100110011110
+010011100100
+110101110100
+000000110010
+001111101100
+010011010010
+010000100000
+110001000100
+110110111111
+011100001111
+110110001101
+111110000010
+010001110010
+001101110101
+111111101101
+010101101101
+001011011100
+001011000001
+001011011101
+010001100010
+011110110011
+000101101011
+000110111000
+101101110000
+101011011001
+001001001110
+000001000000
+101011010010
+101110010111
+110011100001
+001011101001
+000000100001
+010000100110
+101111010000
+011000011100
+100011100110
+110111110011
+110010000100
+101110000000
+110010101101
+011101111000
+001111000110
+101001011100
+011111001111
+111011101010
+001110101110
+101001000011
+111101101111
+111001110101
+000110100110
+111111011011
+101011011011
+111100101101
+111111010100
+101010010000
+101000110011
+011110100000
+010100101001
+010011100011
+101000111001
+101100000111
+101010100010
+101110011111
+111011011110
+110011011001
+101001101101
+110010001011
+010100101000
+001010011010
+001100000000
+110000010000
+000110111011
+011101111111
+011001001001
+011011001001
+000100101001
+110010010010
+000110001001
+001000100011
+101011101111
+100111110010
+110010101011
+000000110110
+010111001101
+100100001111
+100010001011
+011101100100
+000011111000
+010100111011
+010101101100
+100110100110
+110100101110
+010111111001
+010010011110
+111110000100
+000110001101
+100100100001
+111011010111
+101001010101
+111011010010
+101001000000
+100111101100
+101010110000
+000111001101
+000100100110
+100100101000
+111000011001
+000110110101
+111010000011
+101100110001
+000001011000
+001110110011
+101000100110
+100110100101
+010001000111
+100011010001
+010100011101
+110100110110
+100010100110
+101100010001
+010011000100
+100100010101
+110000101101
+010101001100
+100011100100
+001111010100
+100111001001
+110000100000
+100100010111
+010101000010
+101101001010
+110101111101
+010100000110
+011101100110
+011011010010
diff --git a/2021/day3/input.example b/2021/day3/input.example
new file mode 100644
index 0000000..a6366a8
--- /dev/null
+++ b/2021/day3/input.example
@@ -0,0 +1,12 @@
+00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010
diff --git a/2021/day3/src/main.rs b/2021/day3/src/main.rs
new file mode 100644
index 0000000..2440a39
--- /dev/null
+++ b/2021/day3/src/main.rs
@@ -0,0 +1,99 @@
+use std::env;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    if args.len() != 2 {
+        eprintln!("Usage: {} filename", args[0]);
+        std::process::exit(1);
+    }
+    let filename = &args[1];
+    let file = File::open(filename).unwrap_or_else(|_| panic!("No such file: {}", filename));
+    let reader = BufReader::new(file);
+    let mut numbers: Vec<u32> = Vec::new();
+    for line in reader.lines() {
+        let line = line.unwrap();
+        numbers.push(isize::from_str_radix(&line, 2).unwrap().try_into().unwrap());
+    }
+    let mut co2_numbers: Vec<u32> = numbers.clone();
+    let mut oxygen: u32 = 0;
+    let mut co2: u32 = 0;
+    for bit in (0..12).rev() {
+        let keep;
+        let mut one_bits = 0;
+        let mut zero_bits = 0;
+        for num in &numbers {
+            one_bits += (num >> bit) & 1;
+            zero_bits += ((num >> bit) & 1) ^ 1;
+        }
+        println!("for bit: {}", bit);
+        println!("one_bits: {}", one_bits);
+        println!("zero_bits: {}", zero_bits);
+        if zero_bits > one_bits {
+            keep = 0;
+        } else if zero_bits < one_bits {
+            keep = 1;
+        } else {
+            keep = 1;
+        }
+        println!("keeping {}", keep);
+        numbers.retain(|num| ((num >> bit) & 1) == keep);
+        if numbers.len() == 1 {
+            oxygen = numbers.pop().unwrap();
+            break;
+        }
+        println!("{:?}", numbers);
+    }
+    println!("====co2 now====");
+    for bit in (0..12).rev() {
+        let keep;
+        let mut one_bits = 0;
+        let mut zero_bits = 0;
+        for num in &co2_numbers {
+            one_bits += (num >> bit) & 1;
+            zero_bits += ((num >> bit) & 1) ^ 1;
+        }
+        println!("for bit: {}", bit);
+        println!("one_bits: {}", one_bits);
+        println!("zero_bits: {}", zero_bits);
+        if zero_bits > one_bits {
+            keep = 1;
+        } else if zero_bits < one_bits {
+            keep = 0;
+        } else {
+            keep = 0;
+        }
+        println!("keeping {}", keep);
+        co2_numbers.retain(|num| (num >> bit) & 1 == keep);
+        if co2_numbers.len() == 1 {
+            co2 = co2_numbers.pop().unwrap();
+            break;
+        }
+        println!("{:?}", co2_numbers);
+    }
+    println!("oxygen: {}\nco2: {}", oxygen, co2);
+    println!("answer: {}", oxygen * co2);
+}
diff --git a/2021/day4/Cargo.toml b/2021/day4/Cargo.toml
new file mode 100644
index 0000000..8842130
--- /dev/null
+++ b/2021/day4/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "day4"
+version = "0.1.0"
+edition = "2021"
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[dependencies]
diff --git a/2021/day4/input b/2021/day4/input
new file mode 100644
index 0000000..33aa45f
--- /dev/null
+++ b/2021/day4/input
@@ -0,0 +1,601 @@
+84,28,29,75,58,71,26,6,73,74,41,39,87,37,16,79,55,60,62,80,64,95,46,15,5,47,2,35,32,78,89,90,96,33,4,69,42,30,54,85,65,83,44,63,20,17,66,81,67,77,36,68,82,93,10,25,9,34,24,72,91,88,11,38,3,45,14,56,22,61,97,27,12,48,18,1,31,98,86,19,99,92,8,43,52,23,21,0,7,50,57,70,49,13,51,40,76,94,53,59
+31 93 46 11 30
+ 2 45 40 69 33
+82 21 37 99 86
+57 16 34 94 85
+60 49 28 14 65
+96  2 20 41 24
+29 15 27 83 48
+ 7 93 99 82 26
+ 3 91 66 35 85
+62 78 67  4 22
+10 87 50 84 40
+78  5 17 59 44
+38 88 15 46 32
+ 8 72 74 90 23
+64 93 49 39 20
+25 41 32 30 39
+ 6 66 38 95  5
+31 13 56 67 34
+69 18 64 44 96
+75 14 88 97 40
+39 62 50 10 68
+18  7 95 72 82
+83 23 19 70 71
+11 64 30  8  3
+ 6 81 27 34 99
+40 52 66 20 49
+93 74 16 35 29
+97 88  6 98 81
+62 55 99 47 12
+83 76 57 75 22
+52 76 43 86 99
+58 26 61 36 42
+11 69 65  3 49
+33  7 71  8 25
+50 82 32 16 64
+45 38 88 96  8
+22 17  5 60 66
+87 12 61 59  2
+ 0 37 18 15 98
+ 7 62 23 56 92
+20  7 12 26 69
+81 63 89 57 19
+18 44 61 64 53
+47 27  8 30  0
+60 99 28  6 96
+70 50 63 56 26
+55 97 65  5 96
+72 68 29 91 61
+34  0 14 28  4
+45 53 78 80 47
+19 12 92 80 97
+22 37 38  9 82
+86 72 99 59 89
+73 18 21 87 46
+33 77 71 54 94
+66 99 10 44 48
+38 45  4 63 62
+50 27 88 56 89
+81 91 72 90 32
+76 29 17  6  7
+71 39 10 77 50
+97 95 90 98  4
+66 32 73 35 16
+ 1 99  7 96 23
+74 31 94 37  5
+20 72 78  5 69
+88  8 55 80 30
+62 58  4 53 47
+45 13  7 14 52
+86 12 66 74 76
+95 53 59 68 37
+63 40 20 46 43
+ 5 27 67 84 39
+99 51 12 76 50
+78 23 89 22 57
+ 0 96  2 88 11
+98 52 70 28 22
+60 50 18 49 41
+97  6 68 21 47
+90 57 58 99 48
+ 7  3 77 61 34
+57 69 64 68 58
+ 8 49 33 22 15
+63 10  4 95 59
+28 20 71 44 75
+90 68 15 99 38
+16 80 56 70  3
+88 52 18  4 39
+40 85 89 84 44
+65 73 71 79  2
+66 43 12 10 70
+79 57 54 41  6
+46 73 40  3 52
+36 21 38  8 62
+ 7 26 42 32  0
+57 51 69 34 43
+14  9 96 88 74
+90 22 83 30 71
+80 64 91 48 97
+54 38 89 66 16
+51  4 49  2 59
+53 40 33 54 45
+69 41 92 26 60
+93 72 94 90 35
+76  8 75 38 52
+ 5 75 19 28 39
+14 80 27 64 78
+24 69 23 96 42
+ 0 81 10 20 13
+36 57 17 76 52
+38 25  7 88 33
+24 41 96 85 64
+52 89 63 93 18
+94 20  0 98 28
+ 9 30 27 79 83
+74 97 15 55 67
+92 28 24 11 38
+ 8 70 65 63 45
+83 22 30 76 96
+21 85 29 59 36
+ 1 79 29  0 75
+68 58 61 84 51
+85 74 46 69  3
+94 16 41 43 15
+57 21 48 22 42
+61  5  1 25 28
+50 40 74 14 94
+32  0 68 15 54
+60 45 51 31 97
+56 52  8  9 63
+20 36 72 74 83
+ 4 88 35 62 24
+68 39 58 30 34
+61 41 42 93 66
+48 12 57  6 11
+89 52 47 66 64
+67 28 30 46 22
+44 79 23 86 80
+81 25 10 53 94
+56 87 74 60 75
+38 62 76 43 50
+83 53 64  4 44
+52 47 91 49  7
+ 0 85 96 78 86
+32  8 81 87 90
+76 67 31 74 87
+15 70  9 83 78
+60 46 86 73 72
+71 53 82 89 28
+39 97 68 96 11
+88  7 32 40 94
+39 68 13  6  9
+20 55 72 49 25
+56 86 78 12 18
+27 34 19 48 44
+88 19 29 87 28
+53 47 40 74 77
+ 3 93 14 38 33
+78 39 26 32 22
+75  0  2 95 54
+52 35 43 77 79
+53 56 93 92 12
+15 23 16 10 66
+63 96 58 60 94
+ 6 55 76 21 89
+55 11 26 37 18
+77 80  0 30 58
+ 2 97 13 27 98
+68 40 91 56 20
+78 42 45 87 24
+62 71 79 12 66
+ 9 73 30 70 88
+18 72 27  5 75
+49  3 47 33  6
+55 63 98 15 21
+20 52 46 33 27
+80  2 48 29 62
+ 9 32  5 41 53
+74 39 87 12 73
+96 79 61 63 22
+30 48 26 21 83
+56 94 39 47 99
+93 66 25 76 57
+60 96 62 13 84
+71 42 28 31 20
+30 77 49 36 34
+53 75 11 38 61
+41 72  4 58 92
+91 10 21 51 31
+89 43 14 23 45
+30 76 12  1 21
+31  0 82  2  8
+26 28 61 32 99
+65 46 16 39 74
+60 63  5 50 42
+31 90 72 81  8
+17 94 45 20 38
+30 28 68  0 25
+84 10 37 61 83
+87 70 32 64 99
+21 28 99 30  2
+86 64 53 54 84
+82 13 79 96 55
+76  3 12 92 98
+27 89 10 37 95
+74 38 98 18 55
+62 82 93 85 46
+43  3 26 84 86
+97  1 19 12 67
+94 72 68 88  0
+41 97 88  0 40
+20  5 51 42 87
+38  9 11 50  6
+35 25 54 12 81
+75 58 57 94 26
+ 2 30 22 48 88
+60 86 69 31 57
+97 58 95 47 71
+85 63 81 80 73
+25 92 62 11 83
+ 3 93 20 74 86
+21 31 73 35 91
+41 28 25  4 92
+19  5 38 52 59
+37 16 48 85 68
+26 32 66 93 68
+74 90 70 41 57
+99 94 51  3 46
+ 1 24 17 54 39
+53 60 50 96 49
+50 27 72 42 84
+82 62 39 33 31
+99  4 20  3 70
+11 28 57 55 12
+61 29 14 60 90
+60 23 66 99  3
+ 6 24 42 51 45
+41 39 53 25 72
+32 57  5 74  4
+78 44 67  7 50
+ 8 39  4 42 50
+27 25 77 94 90
+52 45 59 60 84
+ 0 78 36 86 22
+56  1 71 82 29
+78 11 49 67 93
+99 76 12 37  1
+17 35 19 92 91
+22 54 31 72 36
+61 96 63 26 33
+ 1 69 71 21 72
+87 92 32 29 80
+40 39 52 42 75
+26 24 11 44 23
+10 99 62 36 98
+60 47 49 24 66
+ 2 19 38 57 94
+54 22 17 33 42
+65 80 48 86 20
+53 27 59 30 11
+ 3 81 64 69 82
+93 80 71 51 46
+76  7 38 57 91
+37 88  8 65 54
+36 25  1 95 77
+75 56 19 21 34
+15  7 24 41 86
+68 29 85 80 88
+18 58 81 44 62
+ 0 52 89 47 59
+49 98 57 90 46
+76 88 84 60  6
+38 78 77 83 99
+79 48  5 63 74
+66 30 37  4 47
+56 37 93 43 11
+81 87 85 52 94
+64 91 36 97 27
+18 31 26 22 78
+50 54 32 69 96
+73 20 51 50 30
+48 83 22 76 85
+26  3 63 67 92
+97  0 87 88  1
+18 33 86 77 52
+ 1 18 50  7 22
+11 96 47 94 67
+58 36 43 65  6
+91 53 23 34 44
+81 30 83 86 55
+ 1 36 10 84 90
+55 35 74 23 26
+29 53 76 40 85
+89 77 16 17 93
+11 19 65  5 49
+99 48 88 10 79
+84 75 66 74 58
+ 3 26 92 91 86
+87 98 52 45 21
+56 51  0 85 69
+53 45 75  5 82
+44 90 11  2 85
+69 19 46 89 47
+ 4 22 16 84 52
+81  1 39  9 38
+18 57 15 30 35
+ 9 32 52 44 25
+69 43 61  3 51
+ 2  8 80 85 33
+72 13 45 10 87
+52 24 26 74 49
+ 0 37 61 91 54
+70 96 60 80 39
+11 75 85 46 18
+16 90 20 66 67
+13 74 92 11  7
+59 46 41 12 55
+27 77 89 70 96
+81  5 29 32 51
+84 75 33 63 99
+87 58 84  6 68
+65  9 75 48 90
+41 94 89 64 21
+95 81 72 32 30
+83 17 63 52 97
+89  0 61 92 16
+44 65 25 66 20
+29 27 37 94 68
+10 63 12 48 77
+ 6 32 82  4 40
+ 1 20 69 80 45
+ 8  7 15 27 19
+40 87  2 98 32
+35 79 84 71 14
+24 43 23 29  6
+59 62 32 74 58
+78 61 85  4 75
+40 30 24 31 46
+89 39 23 63 37
+45 29 44 21 19
+88 44 39 81 43
+26 18 10 73  3
+62 63 74 53 60
+ 0 65 84 54 21
+14 25 76 13  2
+61 57 77  0 92
+12 27 68 89 72
+86 21 44 43 40
+41 74 26 73 66
+ 9 59 32  3  8
+20 93 99 67 28
+53 52 19 72 23
+31 65 25 88 10
+61 37 43  9 76
+60 33 87  3 96
+83 15 46 70 80
+90 69  1  6 64
+43 33 17 99 53
+98 25 30  8 31
+66 94 13 12 75
+18 52 83  3 19
+41 51 60 13 54
+33  5 69 99  8
+27 44 31 34  4
+17 25  1 68 79
+92 23 93 26 75
+50 28 30 42 25
+77 83 56 95 34
+57 13 27 65 81
+ 7 71 40 94  9
+16 28  3 39 82
+ 7 99 44 69  8
+49 51 93 34  6
+60 84  0 92  2
+76 88 38 68 24
+23 99 47 36 77
+20 90  4 78 93
+71 88 52 28 92
+97 31 25 95 39
+ 6 21 68 45 53
+ 0 51 69 75 56
+10 47 12 52  6
+65 87 77 85 42
+98 23 25 97 30
+84 86 67 35 22
+24 36 70 99 98
+94  1 59 67 35
+81 25  6 61 68
+72 53  9 40 92
+97 73 91 41 10
+ 1 78  3 66 15
+39 29 24 76 98
+10 25 90 30 55
+41 96 83 72 51
+46 87 42 26 44
+20 60 59  4 21
+50 71 45 31  1
+49 75 37 54 28
+84 46 98 24  2
+96 16 51 79 35
+59 46 65 39 95
+92  5 10 63 36
+16 90 56 89 70
+83 45 24 64 74
+55 27 54  2 51
+16 23 63 62 57
+17 26 58 83 60
+39 68 22 98 48
+65 50 76  3 14
+24 75 25  7 86
+35 26 74 81 56
+62 84 34 30 33
+ 5 73 21 15 93
+78 77 69 49 43
+44 11 54 51 87
+56 78 74 24 39
+70 85  6 84  9
+97 65 16 82  5
+ 2 12 20 79 42
+14 37 15 69 26
+42 31 88 46 71
+65 97 11 34 48
+85 96 27  0  7
+41  9  5 72 53
+37 93 98 57 64
+ 1 10 55 57 99
+61 92 82 86 56
+19 16 43 84 87
+42  6 79 46 17
+51 44 64 73 35
+17  0 84 15 34
+57 92 41 82 40
+ 8 38 16 35  4
+ 6 33 79 97 96
+52 11 21 10 73
+89  2 81 22 34
+77 87 84 11 80
+85 67 96 49 40
+19  3 76 98 16
+29  1 20 35 82
+ 4 57 84 91  6
+ 8 16 69  1  0
+73  2 41 20  5
+98 40 96 82 93
+12 51 23 68 83
+64 52 50  1 94
+97 58 24 90  5
+ 9 75  3 61 37
+84 91 34 29  8
+30 74  4 18 45
+92 63 96 34  9
+14 25 89  4 98
+23 67 90 74 77
+61  3 93 55 82
+51 65 48 36  8
+70 65 20 76 50
+17  1 33 15 22
+ 3 98 44 91 55
+59 83  2 67 87
+14 63 56 86 37
+61 53 45 88 36
+96 74 15 39 42
+32 55 44 46 86
+79 94 27 54 57
+65  3 21 17 75
+14 26 18 54 20
+24 22 90  0 16
+70 28 33 12 27
+45 95 30 65 75
+19 81 39  2 84
+48 23 67 75 86
+40 46 87 27 93
+79 44 13  3 53
+24 98 54 34  8
+49  1 39 28 35
+ 3 29 16  5 80
+86 50  6 45 88
+22 71 73 34 94
+81 28 68 20 30
+33 37 95 35 57
+49  1  6 26 30
+56  5 63 79 15
+34 52 87 19 66
+59 96 80 42 58
+50 32 72 38 74
+83 90 18 23 64
+87 89 62 31 66
+81 49  9  8 56
+51 85 63 32 50
+95 47 11 98 17
+68 83 80 25 48
+72 39  7 20 30
+32 38 12 66 64
+29 10 44 23 45
+58 15 91 81 95
+90 67 30 22 58
+35 50 63 59 19
+54  4 41 38 65
+43 47 56 96 20
+87 57 33 37 49
diff --git a/2021/day4/input.example b/2021/day4/input.example
new file mode 100644
index 0000000..669a51d
--- /dev/null
+++ b/2021/day4/input.example
@@ -0,0 +1,19 @@
+7,4,9,5,11,17,23,2,0,14,21,24,10,16,13,6,15,25,12,22,18,20,8,19,3,26,1
+22 13 17 11  0
+ 8  2 23  4 24
+21  9 14 16  7
+ 6 10  3 18  5
+ 1 12 20 15 19
+ 3 15  0  2 22
+ 9 18 13 17  5
+19  8  7 25 23
+20 11 10 24  4
+14 21 16 12  6
+14 21 17 24  4
+10 16 15  9 19
+18  8 23 26 20
+22 11 13  6  5
+ 2  0 12  3  7
diff --git a/2021/day4/src/main.rs b/2021/day4/src/main.rs
new file mode 100644
index 0000000..4b6150f
--- /dev/null
+++ b/2021/day4/src/main.rs
@@ -0,0 +1,99 @@
+use std::env;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    if args.len() != 2 {
+        eprintln!("Usage: {} filename", args[0]);
+        std::process::exit(1);
+    }
+    let filename = &args[1];
+    let file = File::open(filename).unwrap_or_else(|_| panic!("No such file: {}", filename));
+    let reader = BufReader::new(file);
+    let mut fd = reader.lines();
+    let mut called_numbers: Vec<i32> = Vec::new();
+    if let Ok(called_nums) = fd.next().unwrap() {
+        called_numbers = called_nums.split(",").map(|x| x.parse().unwrap()).collect();
+    }
+    fd.next(); /* Skip the empty line */
+    let mut boards: Vec<(Vec<(i32, bool)>, bool)> = Vec::new();
+    'outer: loop {
+        let mut miniboard: Vec<(i32, bool)> = Vec::new();
+        for _ in 0..5 {
+            /* New Board */
+            if let Some(maybe_line) = fd.next() {
+                if let Ok(line) = maybe_line {
+                    for (a, b) in line
+                        .split_whitespace()
+                        .map(|x| x.parse().unwrap())
+                        .zip([false].iter().cycle())
+                    {
+                        miniboard.push((a, *b));
+                    }
+                }
+            } else {
+                break 'outer;
+            }
+        }
+        boards.push((miniboard.clone(), false));
+        fd.next(); /* Skip the empty line */
+    }
+    for bingo in called_numbers {
+        for (board, _) in boards.iter_mut() {
+            for (num, mark) in board.iter_mut() {
+                if *num == bingo {
+                    *mark = true;
+                }
+            }
+        }
+        let mut count;
+        for (board, won) in boards.iter_mut() {
+            for row in 0..5 {
+                count = 0;
+                for i in row * 5..(row * 5) + 5 {
+                    if board[i].1 {
+                        count += 1;
+                    }
+                }
+                if count == 5 {
+                    *won = true;
+                }
+            }
+            for column in 0..5 {
+                count = 0;
+                for i in (0..5).map(|x| 5 * x + column) {
+                    if board[i].1 {
+                        count += 1;
+                    }
+                }
+                if count == 5 {
+                    *won = true;
+                }
+            }
+        }
+        if boards.len() == 1 {
+            let mut score: i32 = 0;
+            if let Some(board) = boards.get(0) {
+                for (winnynum, marked) in board.0.iter() {
+                    if !marked {
+                        score += winnynum;
+                    }
+                }
+                println!("score: {}", score * bingo);
+            }
+        }
+        boards.retain(|x| !x.1);
+    }
+}