二分查找算法代码：

#include<iostream>  
using namespace std;  
//非递归实现  
int FindElement(int a[],int first,int end,int target)  
{  
    int mid,value;  
    int L=first,R=end;  
    while(L<R)  
    {  
        mid=(L+R)/2;  
        value=a[mid];  
        if(value==target)  
        {  
            return mid;  
        }  
        if(target<value)  
        {  
			if(R-L==1)
			{
				return -1;
			}
            R=mid;  
        }  
        else  
        {  
			if(a[R]==target)
			{
				return target;
			}
			if(R-L==1)
			{
				return -1;
			}
            L=mid;  
        }  
    }  
    return -1;  
}  
//递归实现  
int Findelement(int a[],int first,int end,int target)  
{  
    int mid;  
    int L=first,R=end;  
    mid=(L+R)/2;  
    if(a[mid]==target)  
    {  
        return mid;  
    }  
    if(mid==end||mid==0)  
    {  
        return -1;  
    }  
    if(a[mid]>target)  
    {  
		if(a[R]==target)
		{
			return target;
		}
        R=mid;  
        return Findelement(a,L,R,target);  
    }  
    else  
    {  if(R-L==1)
		{
			return -1;
		}
		
        L=mid;  
        return Findelement(a,L,R,target);  
    }  
}  
int main()  
{  
    int a[10];  
    for(int i=0;i<10;i++)  
    {  
        a[i]=i*2;  
    }  
    int n=Findelement(a,0,10,7);  
    if(n>=0&&n<10)  
        cout<<a[n];
	else
		cout<<"can't find this element!"<<endl;
    cout<<endl;  
    n=FindElement(a,0,10,7);  
    if(n>=0&&n<10)  
        cout<<a[n];
	else 
		cout<<"can't find this element!"<<endl;
    return 0;  
}