1 files changed, 73 insertions, 0 deletions

diff --git a/2021/day1/depth.c b/2021/day1/depth.c
new file mode 100644
index 0000000..eff19b4
--- /dev/null
+++ b/2021/day1/depth.c
@@ -0,0 +1,73 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+
+int main(int argc, char *argv[])
+{
+        if (argc != 2) {
+                printf("Usage: ./depth <input-file>\n");
+                exit(EXIT_FAILURE);
+        }
+
+        FILE *fp;
+        char *buffer;
+        ssize_t read;
+        size_t len = 0;
+
+        fp = fopen(argv[1], "r");
+        if (fp == NULL) {
+                perror("fopen");
+                exit(EXIT_FAILURE);
+        }
+
+        int inc = 0;
+        int curr = 0;
+        uint8_t idx = 0;
+        int side = 0;
+        int depth[3] = { 0, 0, 0 };
+
+        read = getline(&buffer, &len, fp);
+        if (read != -1) {
+                depth[0] = atoi(buffer);
+        }
+
+        read = getline(&buffer, &len, fp);
+        if (read != -1) {
+                curr = atoi(buffer);
+                depth[0] += curr;
+                depth[1] = curr;
+        }
+
+        read = getline(&buffer, &len, fp);
+        if (read != -1) {
+                curr = atoi(buffer);
+                depth[0] += curr;
+                depth[1] += curr;
+                depth[2] = curr;
+        }
+
+        while ((read = getline(&buffer, &len, fp)) != -1) {
+                side = depth[idx];
+                depth[idx] = 0;
+                idx = (idx + 1) % 3;
+
+                curr = atoi(buffer);
+                depth[0] += curr;
+                depth[1] += curr;
+                depth[2] += curr;
+
+                if (depth[idx] > side) {
+                        inc++;
+                }
+        }
+
+        fclose(fp);
+        if (buffer) {
+                free(buffer);
+        }
+
+        printf("%d", inc);
+
+        return 0;
+}