4.2 谓词

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

class GreaterFive
{
public:
	bool operator()(int val)
	{
		return val > 5;
	}
};
void test01()
{
	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的数子
	//GreatFive() 匿名函数对象
	vector<int>::iterator it = find_if (v.begin(),v.end(),GreaterFive());
	if (it == v.end())
	{
		cout << "未找到" << endl;
	}
	else
	{
		cout << "找到了大于5的数字为：" << *it << endl;
	}
}
int main()
{
	test01();
	system("pause");
	return 0;
}










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

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

class MyCompare
{
public:
	bool operator()(int val1,int val2)
	{
		return val1 > val2;
	}
};

void test01()
{
	vector<int> v;
	v.push_back(10);
	v.push_back(40);
	v.push_back(50);
	v.push_back(30);
	v.push_back(20);
	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
	sort(v.begin(),v.end(),MyCompare());
	for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;
	
}

int main()
{
	test01();
	system("pause");
	return 0;
}