C++之谓词

一元谓词

#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
//仿函数 返回值类型是boo1数据类型，称为谓词
//一元谓词

class GreaterFive
{
public:
	bool operator()(int val)
	{
		return val > 5;
	}
};

void test()
{
	vector<int>v;
	for (int i = 0; i< 10; i++)
	{
		v.push_back(i);
	}

	//查找容器中有没有大于5的值
	///GreaterFive() 名函数对象
	vector<int>::iterator it =  find_if(v.begin(), v.end(), GreaterFive());
	if (it == v.end())
	{
		cout << "没有找大于5的数字" << endl;
	}
	else
	{
		cout << "找到了大于5的数字为：" << *it << endl;
	}
}


int main()
{
	test();

	system("pause");
	return 0;
}

二元谓词

#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
//仿函数 返回值类型是boo1数据类型，称为谓词
//二元谓词

class MyCompare
{
public:
	bool operator()(int v1,int v2)
	{
		return v1 > v2;
	}
};

void test()
{
	vector<int>v;
	v.push_back(10);
	v.push_back(50);
	v.push_back(20);
	v.push_back(30);
	v.push_back(40);

	sort(v.begin(), v.end());
	for (vector<int>::iterator it = v.begin();it != v.end();it++)
	{
		cout << *it << " ";
	}
	cout << endl;
	使用函数对象 改变算法策略，变为排序规则为从大到小
	cout << "--------------------" << endl;
	sort(v.begin(), v.end(), MyCompare());
	for (vector<int>::iterator it = v.begin();it != v.end();it++)
	{
		cout << *it << " ";
	}
	cout << endl;
}


int main()
{
	test();

	system("pause");
	return 0;
}