Update 02. As Many Transactions As You Like.py

02_Dynamic-Programming/11. Buy and Sell Stock Problems/02. As Many Transactions As You Like.py

@@ -1,4 +1,41 @@
 # https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/
+# https://www.youtube.com/watch?v=nGJmxkUJQGs
+
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        memo = {}
+        def solve(i, can_sell):
+            if i == len(prices): 
+                return 0
+            if (i, can_sell) in memo: 
+                return memo[(i, can_sell)]
+            if can_sell == 1:
+                profit = max(prices[i] + solve(i+1, 0), solve(i+1, 1))
+            else:
+                profit = max(-prices[i] + solve(i+1, 1), solve(i+1, 0))
+            memo[(i, can_sell)] = profit
+            return profit
+        return solve(0, 0)
+
+# Time: O(2 * N)
+# Space: O(N + N)
+
+################################################################################################
+
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        n = len(prices)
+        dp = [[0]*2 for _ in range(n+1)]
+        dp[0][0] = -2**31
+        for i in range(1, n+1):
+            for can_sell in range(2):
+                if can_sell == 1:
+                    dp[i][can_sell] = max(prices[i-1] + dp[i-1][0], dp[i-1][1])
+                else:
+                    dp[i][can_sell] = max(-prices[i-1] + dp[i-1][1], dp[i-1][0])
+        return dp[-1][1]
+
+################################################################################################
 
 class Solution:
     def maxProfit(self, prices):