day1: add python part1

2020/day1/day1.py

@@ -0,0 +1,15 @@
+#!/usr/bin/env python
+import sys
+from typing import Iterable
+
+def find2020(nums: Iterable[int]) -> int:
+    candidates = set()
+    for num in nums:
+        opposite = 2020-num
+        if num in candidates:
+            return num * opposite
+        candidates.add(opposite)
+
+if __name__ == '__main__':
+    with open(sys.argv[1], 'r') as f:
+        print(find2020(int(n) for n in f.readlines()))