【leetcode】Maximum Subarray

 1 class Solution {
 2 public:
 3     int maxSubArray(int A[], int n) {
 4         if(n<=0) return 0;
 5         
 6         int sum=0;
 7         int max=INT_MIN;
 8         
 9         
10         for(int i=0;i<n;i++)
11         {
12             sum+=A[i];
13             if(sum>max) max=sum;
14             if(sum<0) sum=0;
15             
16         }
17         return max;
18     }
19 };

 1 int myMaxSubArray(int A[], int m, int n)
 2 {
 3     if (m == n) return A[m];
 4 
 5     int mid = (m+n)/2;
 6     int maxPre = myMaxSubArray(A, m, mid);
 7     int maxEnd = myMaxSubArray(A, mid+1, n);
 8 
 9     int leftMax = INT_MIN;
10     int rightMax = INT_MIN;
11     int sum = 0;
12     for (int i = mid; i >= m; i--)
13     {
14         sum += A[i];
15         if (sum > leftMax)
16             leftMax = sum;
17     }
18     sum = 0;
19     for (int i = mid+1; i <=n; i++)
20     {
21         sum += A[i];
22         if (sum > rightMax)
23             rightMax = sum;
24     }
25     sum = leftMax + rightMax;
26 
27     return std::max(sum, std::max(maxPre, maxEnd));
28 }
29 
30 int maxSubArray(int A[], int n) 
31 {
32     if (n <= 0) return 0;
33 
34     return myMaxSubArray(A, 0, n-1);
35 }