leetcode 53. Maximum Subarray

leetcode 53. Maximum Subarray

链接

leetcode

描述

Given 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.

solution

solution1 在线处理

思路：用maxSum记录最大子列和，用thisSum记录当前处理的和，如果发现当前子列和未负，则舍弃。

class Solution {
public:
    int maxSubArray(vector<int>& nums) {

        int maxSum = -2147483648, thisSum = 0;
        for(int i = 0; i < nums.size(); i++)
        {
            thisSum += nums[i];
            if(thisSum > maxSum)
                maxSum = thisSum;
           if( thisSum < 0)
                thisSum = 0;
        }
        return maxSum;

    }
};

分析：
时间复杂度：O(N)
空间复杂度:O(1)