查找-折半查找

给定一个有序序列,查找与key相等的值,如果没有则返回-1(注意这里不要返回0,会和数组下标重复)

#include 

int binary_search(int a[],int left,int right,int key)
{
    while(left <= right)
    {
        int mid = (left + right) /2;
        if(a[mid] == key)
            return mid;
        else if(a[mid] < key)
        {
            left = mid + 1;
        }
        else
        {
            right = mid -1;
        }
    }
    return -1;
}
int main()
{
    int a[] = {1,2,3,4,5,6,7,8};
    int index;
    int right = sizeof(a)/sizeof(int);
    index = binary_search(a,0,right-1,3);
    printf("%d",index);
    return 0;
}