[LeetCode系列]最大连续子列递归求解分析

 1 class Solution {
 2 public:
 3     int maxSubArray(int A[], int n) {
 4         // IMPORTANT: Please reset any member data you declared, as
 5         // the same Solution instance will be reused for each test case.
 6         if(n==0) return 0;
 7         return maxSubArrayHelperFunction(A,0,n-1);
 8     }
 9 
10     int maxSubArrayHelperFunction(int A[], int left, int right) {
11         if(right == left) return A[left];
12         int middle = (left+right)/2;
13         int leftans = maxSubArrayHelperFunction(A, left, middle);
14         int rightans = maxSubArrayHelperFunction(A, middle+1, right);
15         int leftmax = A[middle];
16         int rightmax = A[middle+1];
17         int temp = 0;
18         for(int i=middle;i>=left;i--) {
19             temp += A[i];
20             if(temp > leftmax) leftmax = temp;
21         }
22         temp = 0;
23         for(int i=middle+1;i<=right;i++) {
24             temp += A[i];
25             if(temp > rightmax) rightmax = temp;
26         }
27         return max(max(leftans, rightans),leftmax+rightmax);
28     }
29 };