有序表的折半查找

非递归实现

#include <stdio.h>
int search(int num[],int n,int key)
{
    int low=0;
    int high =n-1;
    int mid=0;
    while(low<=high)
    {
        mid = (low+high)/2;
        if(num[mid]==key)return mid;
        else if(num[mid]<key)
        {
            low=mid+1;
        }
        else 
        {
            high = mid-1;
        }
    }
    return -1;
}
int main()
{
        int a;
        scanf("%d",a);
    int num[10]={0,1,2,3,4,5,6,7,8,9};
    printf("%d\n",search(num,10,a));
    return 0;
}

 

 递归实现

#include <stdio.h>
int search(int num[],int low,int high,int key)
{
    if(low==high&&num[low]!=key)
    {
        return -1;
    }
    int mid=0;
    mid = (low+high)/2;
    if(num[mid]==key)
    {
        return mid;
    }
    else if(num[mid]<key)
    {
        low =mid+1;
    }
    else
    {
        high =mid-1;
    }
    search(num,low,high,key);
}
int main()
{
    int num[10]={0,1,2,3,4,5,6,7,8,9};
    printf("%d\n",search(num,0,9,0));

    return 0;
}