二分搜索和最大子集和

1. 二分搜索

   #include <stdio.h>
   
   int binary_search(int arr[], int left, int right, int key);
   
   int main()
   {
       int arr[10] = {2, 5, 18, 24, 37, 57, 73, 83, 95, 99};/*输入一个数组，数组默认是已经排序好的*/
       int left, right, key;
       int a;
       left = 0;
       right = 10;
       key = 18;
   
       a = binary_search(arr, left, right, key);/*调用二分搜索函数，并将返回值赋给a*/
       
       printf("%d\n", a);
   
       return 0;
   }
   
   int binary_search(const int arr[], int left, int right, int key)
   {
       if (left > right)
           return -1;
       
       int mid = left + (right - left)/2;
       if (arr[mid] > key)
           return binary_search(arr, left, mid - 1, key);
   
       if (arr[mid] < key)
           return binary_search(arr, mid + 1, right, key);
   
       return mid;
   }

2. 最大子区间

3. #include <stdio.h>
   
   int arr[10] = {8, 4, -1, 0, -6, 7, 5, 2, -3, 8};
   
   int main()
   {
       int start = 0;
       int end = 0;
       int max = 0;
       int n = 10;
       int i, j;
       for (i = 0; i < n; i++ )
       {
           int sum = 0;
   	for (j = i; j < n; j++)
   	{
   	    sum = sum + arr[j];
   	    if (sum > max)
   	    {
   	        start = i;
   	        end = j;
    	        max = sum;
               }
           }
       }	
       printf("The max interval arr[%d-%d], and the sum = %d\n", start, end, max);
       return 0;
   }