折半查找非遞歸與遞歸實作：

#include<stdio.h>
int linner(int a[],int n,int value);
int halfSearch(int a[],int n,int value);
int halfSearch2(int a[],int n,int value,int left,int right);
void main()
{
    int a[8]= {12,34,50,53,123,135,167,189};
    // int num=linner(a,8,53);//線性查找
    // int num=halfSearch(a,8,167);   //非遞歸
    int num=halfSearch2(a,8,167,0,7);//遞歸
    if(num==-1)
        printf("沒有找到這個數");
    else
        printf("位置在第：%d",num);
}
int linner(int a[],int n,int value)   //線性查找
{
    for(int i=0; i<n; i++)
        if(a[i]==value)
            return i+1;
    return -1;
}
int halfSearch(int a[],int n,int value)//非遞歸折半查找
{
    int left=0,right=n-1,mid;
    while(left<=right)
    {
        mid=(left+right)/2;
        if(value>a[mid])
            left=mid+1;
        else if(value<a[mid])
            right=mid-1;
        else
            return mid+1;
    }
    return -1;
}
int halfSearch2(int a[],int n,int value,int left,int right) //遞歸折半查找
{
    if(left>right)
        return -1;
    int mid=(left+right)/2;
    if(a[mid]==value)
        return mid+1;
    else if(value>a[mid])
        return halfSearch2(a,n,value,mid+1,right);
    else
        return halfSearch2(a,n,value,left,mid-1);
}