STL中binary_search 演示

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本文通过一个具体的 C++ 程序示例介绍了 STL 中 sort、lower_bound、upper_bound、equal_range 和 binary_search 函数的应用，展示了如何在已排序的 vector 容器中查找特定元素。

#include "StdAfx.h"
#include <iostream> 
#include <fstream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{
    vector<int> v;
    vector<int>::iterator iter;
    pair<vector<int>::iterator, vector<int>::iterator> vecpair;

    for(int i = 1; i<= 20; i++) 
	{
        v.push_back(i%6);
    }
    sort(v.begin(), v.end());
    cout << "array: " << endl << "  ";
    copy(v.begin(), v.end(), ostream_iterator<int>(cout, " "));
    cout << endl << endl;

    /*  lower_bound */
    cout << "lower_bound function, value = 3: " << endl;
    iter = lower_bound(v.begin(), v.end(), 3);
    cout << "  [first, iter] = ";
    copy(v.begin(), iter, ostream_iterator<int>(cout, " "));
    cout << endl;
    cout << "  [iter, last] = ";
    copy(iter, v.end(), ostream_iterator<int>(cout, " "));
    cout << endl << endl;

    /*  upper_bound */
    cout << "upper_bound function, value = 3: " << endl;
    iter = upper_bound(v.begin(), v.end(), 3);
    cout << "  [first, iter] = ";
    copy(v.begin(), iter, ostream_iterator<int>(cout, " "));
    cout << endl;
    cout << "  [iter, last] = ";
    copy(iter, v.end(), ostream_iterator<int>(cout, " "));
    cout << endl << endl;

    /*  equal_range */
    cout << "euqual_range function value = 3: " << endl;
    vecpair = equal_range(v.begin(), v.end(), 3);

    cout << " [vecpair->first, vecpair->second] = ";
    copy(vecpair.first, vecpair.second, ostream_iterator<int>(cout, " "));
    cout << endl << endl;

    /*  binary_search */
    cout << "binary_search function value = 3: " << endl;
    cout << "3 is " << (binary_search(v.begin(), v.end(), 3) ? "": "not ") << " in array" << endl;
    cout << endl;

    /*  binary_search */
    cout << "binary_search function value = 6: " << endl;
    cout << "6 is " << (binary_search(v.begin(), v.end(), 6) ? "": "not ") << " in array" << endl;
    cout << endl;
}

运行结果：