leetcode 53. Maximum Subarray( Python )

描述

iven an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.

Example:

Input: [-2,1,-3,4,-1,2,1,-5,4],
Output: 6
Explanation: [4,-1,2,1] has the largest sum = 6.

Follow up:

If you have figured out the O(n) solution, try coding another solution using the divide and conquer approach, which is more subtle.

解析

根据题意，设置两个变量 l 和 g，l 表示以当前位置结尾的子串的最大值， g 表示的是全局最大值，这个值肯定是来自于若干个 l 值。时间复杂度为 O(N)，空间复杂度为 O(1)。

解答

class Solution(object):
    def maxSubArray(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        l = g = float("-inf")
        for i in nums:
            l = max(l+i,i)
            # print(l)
            g = max(g,l)
        return g      
                   

运行结果

Runtime: 44 ms, faster than 96.59% of Python online submissions for Maximum Subarray.
Memory Usage: 12.2 MB, less than 78.58% of Python online submissions for Maximum Subarray.
	

每日格言：成功的诀窍在于永不改动既定的方针。