[模板题] - 53. 最大子数组和

题目链接	53. 最大子数组和
思路	1. 前缀和 2. 动态规划
题解链接	两种方法：前缀和/动态规划（Python/Java/C++/C/Go/JS/Rust）
关键点	无
时间复杂度	\(O(n)\)
空间复杂度	\(O(1)\)

代码实现（前缀和）：

class Solution:
    def maxSubArray(self, nums: List[int]) -> int:
        answer = -inf
        min_presum = 0
        presum = 0
        for num in nums:
            presum += num
            answer = max(answer, presum - min_presum)
            min_presum = min(min_presum, presum)
        return answer

代码实现（动态规划）：

class Solution:
    def maxSubArray(self, nums: List[int]) -> int:
        answer = -inf
        dp = 0
        for x in nums:
            dp = max(dp, 0) + x
            answer = max(answer, dp)
        return answer