分治算法求解序列最大子和问题

特别的，当序列所有整数均为负整数时，其最大子和为0。

#include <stdio.h>

int caluMaxSubSum(int *array, int left, int right);

int main()
{   
    int array[6] = {2, -2, 3, 1, -4, 2};
    int len_array = sizeof(array)/sizeof(array[0]);
    int i = 0;
    int subsum = caluMaxSubSum(array, 0, len_array);
    for(i = 0; i < len_array; i++)
    {
       printf("%d ", array[i]);
    }
    
    printf("
");
    //printf("最大子和是: ");
    printf("subsum = %d
", subsum);    
    return 0;
}

int caluMaxSubSum(int *array, int left, int right)
{   
   int sum = 0;
   if(left >= right)
   {
      if(array[left] > 0)
      {
          sum  = array[left];
      }
      else
      {   
          sum = 0;  
      }
   }
   else
   {
      int center = (left + right)/2;
      int s1 = 0, s2 = 0;
      int lefts = 0, rights = 0;
      int i = 0;
      int leftsum = caluMaxSubSum(array, left, center);
      int rightsum = caluMaxSubSum(array, center + 1, right);
      for(i = center; i >= left; i--)
      {
         lefts += array[i];
         if(lefts > s1)
         {
             s1 = lefts;
         }
      }
      
      for(i = center + 1; i < right; i++)
      {
          rights += array[i];
          if(rights > s2)
          {
             s2 = rights;
          }          
      }
      
      sum = s1 + s2;
      if(sum < leftsum)
      {
         sum = leftsum;
      }
      if(sum < rightsum)
      {
          sum = rightsum;
      }
   }
   
   return sum;
}

关键性的思路在哪里？