add max profit algorithm

Author: dori-dev

arrays/max_profit.py

@@ -0,0 +1,28 @@
+"""
+buy-sell stock:
+    max_profit([7, 1, 5, 3, 6, 4]) => 5
+    max_profit([9, 7, 6, 4, 3, 1]) => 0
+complexity: O(n)
+"""
+
+from typing import List
+
+
+def max_profit(prices: List[int]) -> int:
+    profitable_stocks = {}
+    for first, second in zip(prices, prices[1:]):
+        distance = second - first
+        if distance > 0:
+            profitable_stocks[(first, second)] = distance
+    if not profitable_stocks:
+        return 0
+    best_match = max(
+        profitable_stocks,
+        key=lambda key: profitable_stocks[key]
+    )
+    return best_match[1]
+
+
+if __name__ == "__main__":
+    print(max_profit([7, 1, 5, 3, 6, 4]) == 5)
+    print(max_profit([9, 7, 6, 4, 3, 1]) == 0)