add remaining code and input files from 2020

AoC2020/code/AoC15.py

@@ -0,0 +1,19 @@
+def next(num, turn, memo):
+    if num not in memo:
+        memo[num] = (0, turn)
+        return 0
+    memo[num] = (memo[num][1], turn)
+    return memo[num][1] - memo[num][0]
+
+
+def solve(input, target):
+    memo, n = {}, input[-1]
+    for i, j in enumerate(input):
+        memo[j] = (0, i)
+    for t in range(len(input)-1, target-1):
+        n = next(n, t, memo)
+    return n
+
+
+print(solve([16, 12, 1, 0, 15, 7, 11], 2020))
+print(solve([16, 12, 1, 0, 15, 7, 11], 30000000))