二分法查找

#ifndef _BINARYSEARCH_H
#define _BINARYSEARCH_H
template<typename Iterator,typename T>
bool binarySearch(Iterator p, Iterator r, Iterator &rp, const T &value)
{
    int n = distance(p, r);
    if (n < 1)
        return false;//无此元素

    Iterator q = p;
    advance(q, n/2);//q=[q+r]/2
    if (*q == value)
    {
        rp = q;
        return true;
    }
    if (*q>value)
        return binarySearch(p, q,rp,value);
    else
        return binarySearch(q+1, r,rp, value);

}
/******************二分法查找*****************
输入;p,q,序列首末地址，
     value:目标查找元素
返回：若找到元素，返回其地址，否则返回last iterator
*********************************************/
template<typename Iterator,typename T>
Iterator binarySearch(Iterator p, Iterator r, const T &value)
{
    static Iterator k = r;//static局部变量，仅做第一次初始化，且在多次调用中保存改变的值
    int n = distance(p, r);
    if (n < 1)
        return k;
    Iterator q = p;
    advance(p, n / 2);
    if (*q == value)
        return q;
    if (*q>value)
        return binarySearch(p, q, value);
    else
        return binarySearch(q + 1, r, value);
}
#endif // !_BINARYSEARCH_H

#include <cstdio>
#include <algorithm>
#include <vector>
#include <iterator>
#include <iostream>
#include "binarySearch.h"
using namespace std;
int main(int argc, char** argv)
{
    int a[] = { 0, 1, 2, 3, 5, 6, 7, 8, 9 };
    int b;
    vector<int> va=vector<int>(a, a+9);
    vector<int>::iterator k;
    //binary_search(va.begin(), va.end(), 0);
    /*if (binarySearch(va.begin(), va.end(), k, 3))
        b = distance(va.begin(), k);
    else
        b = -1;*/
    b = distance( va.begin(),binarySearch(va.begin(), va.end(), 9));
    cout << b << endl;
    system("pause");
}