二分查找的递归和非递归实现

/*
author:justinzhang
email:uestczhangchao@gmail.com
time:2012-8-30 18:54:01
desc: binary search from the aocp p380
*/

#include <iostream>
#include <vector>
#include <memory> //for auto_ptr, but auto_ptr does not support arrays
#include <ctime> // for time(0) function
#include <cstdlib> // for srand and rand function
#include <algorithm> // for sort and binary_search function
using namespace std;

template <class type>
type random(type start, type end)
{
    srand((int)time(0)*rand());
    return (start + (end-start)*rand()/(RAND_MAX+1.0));
}

template<class type> bool my_binary_search(vector<type> data, int begin, int end, type value)
{
    int L = begin;
    int U = end;
    while(U>L) //注意此处不要写成了U>=L,如果是>=，并且数组下标从0开始的话，就会导致vector下标越界
    {
        int M = L+(U-L)/2;
        if(data[M] > value)
            U = M-1;
        else if(data[M] < value)
            L = M+1;
        else
            return true;
    }
    return false;
}

template <class type> bool recursive_binary_search(vector<type> data, int begin, int end, type key)
{
    if(begin >= end)
        return false;
    else
    {
        int mid = begin+(end - begin)/2;
        if(data[mid] > key)
            recursive_binary_search(data,begin,mid-1,key);
        else if(data[mid] < key)
            recursive_binary_search(data,mid+1,end,key);
        else
            return true;
    }
}


int main()
{
    /*auto_ptr does not support for arrays, C11 support*/
    //auto_ptr<double> auto_ptr_data(new double);
    //*auto_ptr_data = 100;
    //cout << *auto_ptr_data << endl;

    vector<double> data;
    for(unsigned int i=0; i<20; i++)
    {
        data.push_back(random<double>(1,10));
    }

    data.push_back(77.77);

    vector<double> copy_data(data.size());
    copy(data.begin(),data.end(),copy_data.begin());

    for(unsigned int i=0; i<10; i++)
    {
        cout << data[i] << "==" << copy_data[i] << endl;
    }

    sort(data.begin(),data.end());
    for(unsigned int i=0; i<data.size(); i++)
    if(binary_search(data.begin(),data.end(),copy_data[i]))
    {
        cout << "found item: " << copy_data[i] << endl;
    }

    /*-----test non-recursive version-----*/
    if(my_binary_search<double>(data,0,data.size(),898))
    {
        cout << " find item: " << 898<< endl;
    }
    else
        cout << "not found item:" << 898 << endl;

    /*----test recursive binary search-----*/
    vector<double> A(10,random(1,10)); //初始化向量A，每一个元素都为1
    for(int i=0; i<10; i++)
        cout << A[i] << endl;
    if(recursive_binary_search<double>(A,1,5,1))
        cout << "found !" << endl;


    return 0;
}