二分查找算法模板

#include<iostream> 
#include<cstdio>
using namespace std;
const int n=4; 
int a[]={0,5,6,8,10};
int erfenEqual(int low,int high,int key)
{
    int mid;
    
    while(low<=high)
    {
    
        mid=(low+high)/2;
        if (a[mid]==key)
            return mid;
        else if(a[mid]>key)
            high=mid-1;
        else
            low=mid+1;
            
    }
    return -1;
} 
int erfenBig(int low,int high,int key)//找到第一个大于Key的元素的位置 
{
    int mid;
    while(low<=high)
    {
        mid=(low+high)/2;
        if(a[mid]>key)
            high=mid-1;
        else
            low=mid+1;
    }
    return low;
} 
int main()
{
    int x=erfenEqual(1,4,8);
    if (x==-1) 
        cout<<"找不到";
    else
        cout<<"找到，位置为"<<x;
    
    x=erfenBig(1,4,8);
    if (x>n) 
        cout<<"在数组中找不到比此数还大的数";
    else
        cout<<"找到，位置为"<<x;
    return 0;
}