53. 最大子序和

Author: chenpengcode

dp/53_maxSubArray.py

@@ -0,0 +1,37 @@
+from typing import List
+
+
+class Solution:
+    def maxSubArray_dp(self, nums: List[int]) -> int:
+        n = len(nums)
+        dp = [nums[0]] * n
+        ans = dp[0]
+        for i in range(1, n):
+            dp[i] = max(dp[i - 1] + nums[i], nums[i])
+            ans = max(dp[i], ans)
+
+        return ans
+
+    def maxSubArray_dp1(self, nums: List[int]) -> int:
+        n = len(nums)
+        ans = cur = nums[0]
+        for i in range(1, n):
+            cur = max(cur + nums[i], nums[i])
+            ans = max(ans, cur)
+        return ans
+
+    def maxSubArray_greed(self, nums: List[int]) -> int:
+        if not nums:
+            return float('-inf')
+        cur_sum = max_sum = nums[0]
+
+        for i in range(1, len(nums)):
+            cur_sum = max(cur_sum + nums[i], nums[i])
+            max_sum = max(cur_sum, max_sum)
+        return max_sum
+
+
+if __name__ == '__main__':
+    nums = [-2, 1, -3, 4, -1, 2, 1, -5, 4]
+    solution = Solution()
+    print(solution.maxSubArray_greed(nums))