1 int binary_search(int* a, int len, int goal) 2 { 3     int low = 0; 4     int high = len - 1; 5     while(low <= high) 6     { 7         int middle = (low + high)/2; 8         if(a[middle] == goal) 9             return middle;10         //在左半边11         else if(a[middle] > goal)12             high = middle - 1;13         //在右半边14         else15             low = middle + 1;16     }17     //没找到18     return -1;19 }