c++ stl algorithm: std::find, std::find_if

转: http://blog.csdn.net/ilysony/article/details/6526545
std::find:

    查找容器元素, find只能查找容器元素为<基本数据类型>

#include <iostream>
#include <vector>
#include <algorithm>
int main()
{
    std::vector<int> v;
    for (int i = 0; i < 10; ++i)
        v.push_back(i);
    std::vector<int>::iterator iter = std::find(v.begin(), v.end(), 3);
    if (iter == v.end())
        std::cout << "can not find value 3 in v" << std::endl;
    else
        std::cout << "the index of value " << (*iter) << " is " << std::distance(v.begin(), iter) << std::endl;
    return 0;
}

std::find_if

    按条件查找容器元素, 容器类型为<类>时, 无法使用find来查找,  所以要使用find_if来查找

#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
struct Point
{
    int x;
    int y;
};
struct PointFindByCoord : public std::binary_function<Point, Point, bool>
{
    bool operator () (const Point &obj1, const Point &obj2) const
    {
        return obj1.x == obj2.x && obj1.y == obj2.y;
    }
};
int main()
{
    std::vector<Point> v;
    for (int i = 0; i < 5; ++i)
    {
        for (int j = 0; j < 5; ++j)
        {
            Point pt;
            pt.x = i;
            pt.y = j;
            v.push_back(pt);
        }
    }
    Point needFind;
    needFind.x = 4;
    needFind.y = 3;
    std::vector<Point>::iterator iter = std::find_if(v.begin(), v.end(), std::bind2nd(PointFindByCoord(), needFind));
    if (iter == v.end())
    {
        // 未找到
    }
    else
        std::cout << "the index of value Point(" << (*iter).x << ", " << (*iter).y
            << ") is " << std::distance(v.begin(), iter) << std::endl;

    return 0;
}

1楼 mcadcj 2014-06-11 14:31发表    怎么可能find不能找类，是你自己的类没有定义operator == 。。。。

自己的类中定义了operator就可以???