二分查找递归

 
int f(int m,int n,int a[],int x)
{
    if(m<=n)
    {
        int mid=(n+m)/2;
        if(a[mid]==x) return mid+1;
        else if(a[mid]<x) return f(mid+1,n,a,x);
         else return f(m,mid-1,a,x);
    }
    else return -1;
}