20140717 二分查找 递归和非递归

1、二分查找代码

二分查找：

#include<iostream>
using namespace std;

int BinarySearch(int a[],int len,int value)//len是a中包含的元素熟练，如a={1,2,3}，那么len=3,
{
    int low=0,hi=len,mid=(low+hi)/2;
    while(low<=hi)
    {
        if(value==a[mid])
        {
            return(a[mid]);
        }
        else if(a[mid]>value)
        {
            hi=mid-1;
        }
        else 
            low=mid+1;
        mid=(low+hi)/2;
    }
    return -1;
}
void main()
{
    int a[]={0,1,2,3,4,5,6,7,8,9};
    int result=BinarySearch(a,9,0);
    //int result=BinarySearch(a,10,9);
    cout<<result<<endl;
}

二分查找递归方法：
int BinarySearch(int *a,int lo,int hi,int value)
{
    if(lo>hi)
        return -1;
    int start=lo,end=hi,mid=(start+end)/2;
    if(a[mid]>value)
        end=mid-1;
    else if(a[mid]<value)
        start=mid+1;
    else
        return a[mid];
    return BinarySearch(a,start,end,value);
        
}