关系仿函数

function:
实现关系对比
仿函数原型：

#include<iostream>
using namespace std;
#include<functional>
#include<vector>
#include<algorithm>
void  p(const vector<int>& v)
{
	for (int i = 0; i < v.size(); i++)
	{
		cout << v[i] << " ";
	}
	cout << endl;
}
class compare {
public:
	bool operator()(int v1, int v2) const
	{
		return v1 > v2;
	}
};
void test()
{
     //1.关系仿函数
	vector<int>  v = { 3,25,67,4,2,7,34,56 };
    //未打印输出前
	cout << "未排序：" << endl;
	p(v);
	cout << "----------------------------" << endl;
	//sort----升序
	sort(v.begin(), v.end());
	cout << "升序：" << endl;
	p(v);
	cout << "--------------------------------" << endl;
	//改变排序规则

	//第一种方法：
	//sort(v.begin(), v.end(),compare());
	//第二种：
	sort(v.begin(), v.end(), greater<int>());
	cout << "降序：" << endl;
	p(v);
	cout << "--------------------------------" << endl;
}
int main()
{
	test();
	system("pause");
	return 0;
}

总结：用的比较多的是大于