1 files changed, 55 insertions, 0 deletions

diff --git a/2020/day8/gamechild.py b/2020/day8/gamechild.py
new file mode 100644
index 0000000..3763c78
--- /dev/null
+++ b/2020/day8/gamechild.py
@@ -0,0 +1,55 @@
+boot_code = list()
+
+
+def gameon(acc, cx, sf):
+    """emulates the game until a loop or the end"""
+
+    while cx not in sf:
+        sf.add(cx)
+
+        if cx == len(boot_code):
+            print(acc)
+            exit(0)
+
+        if boot_code[cx][0] == "acc":
+            acc += boot_code[cx][1]
+        elif boot_code[cx][0] == "jmp":
+            cx += boot_code[cx][1] - 1
+        else:  # nop
+            pass
+
+        cx += 1
+
+
+with open("input", "r") as file:
+    for line in file:
+        line = line.strip()
+        oparg = line.split(" ")
+        boot_code.append((oparg[0], int(oparg[1])))
+
+
+cursor = 0
+accumulator = 0
+sofar = set()
+
+# we are allowed to keep a 'main' branch and keep jmp/nops separate because
+# task calls for only one instruction change over the whole code
+
+while cursor not in sofar:
+    sofar.add(cursor)
+
+    if boot_code[cursor][0] == "acc":
+        accumulator += boot_code[cursor][1]
+    elif boot_code[cursor][0] == "jmp":
+        # one for the jmp
+        gameon(accumulator, cursor + boot_code[cursor][1], sofar.copy())
+        # one for the nop
+        gameon(accumulator, cursor + 1, sofar.copy())
+        cursor += boot_code[cursor][1] - 1
+    elif boot_code[cursor][0] == "nop":
+        # one for the nop
+        gameon(accumulator, cursor + 1, sofar.copy())
+        # one for the jmp
+        gameon(accumulator, cursor + boot_code[cursor][1], sofar.copy())
+
+    cursor += 1