53. Maximum Subarray

 1 static int wing=[]()
 2 {
 3     std::ios::sync_with_stdio(false);
 4     cin.tie(NULL);
 5     return 0;
 6 }();
 7 
 8 class Solution 
 9 {
10 public:
11     int maxSubArray(vector<int>& nums) 
12     {
13         int res=nums[0],i=0,sum=0;
14         int sz=nums.size();
15         while(i<sz)
16         {
17             sum+=nums[i];
18             res=max(res,sum);
19             sum=max(sum,0);
20             ++i;
21         }
22         return res;
23     }
24 };

Scan from front to back, set a variable res to store the result, and a sum to store the current value.

Scan once, accumulate the result to sum, compare sum and res, assign the larger value to res

Then determine sum, and set it to 0 if sum is negative.

Sweep down in this way, res is the sum of the largest substring