LeetCode 53. Maximum Subarray C++

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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.

基于贪心算法

class Solution {
public:
    int maxSubArray(vector<int>& nums) {
        int sum = 0;
        int maxsum = INT_MIN;        

        for (int i = 0; i < nums.size(); i++) {
            if (sum + nums[i] <= 0) {                
                if (maxsum < 0)     //这里加个判断更快
                    maxsum = max(maxsum, nums[i]);
                else
                    sum = 0;
            }
            else {
                sum += nums[i];
                maxsum = max(maxsum, sum);
            }            
        }
        return maxsum;        
    }
};