19 Maximum Subarray

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.

一道很有趣的Easy题目，一开始用暴力算法，果然只比5%的解法快。。。。

class Solution {
public:
    int maxSubArray(vector<int>& nums) {
        
        int len = nums.size();
        
        int sum,max_sum;
        
        max_sum = INT_MIN;
        
        for(int i=0;i<len;i++)
        {
            int sum = 0;
            
            for(int j=i;j<len;j++)
            {
                sum += nums[j];
                if(sum > max_sum) max_sum = sum;
            }
        }

        
        return max_sum;
        
    }
    
    
};

去评论区参考了一下更优解，果然颜值就是战斗力，简洁美观的代码效果一般都很不错。。。
for循环中头两句比较清楚明白，最后一句是关键，它可以自动抛弃和为负数的部分。

class Solution {
public:
    int maxSubArray(vector<int>& nums) {
        
        int len = nums.size();
        
        int sum,max_sum;
        
        max_sum = INT_MIN;
        sum = 0;
        
        for(int i=0;i<len;i++)
        {
            sum += nums[i];
            max_sum = max(max_sum, sum);
            sum = max(sum,0);
        }
        
        return max_sum;
        
    }
    
    
};