C++ sort排序之降序、升序使用总结

struct Student{
 string name;
 int grade;
 
 Student(string name, int grade) : name(name), grade(grade){}
 
 bool operator < (const Student& rhs) const{
  return grade < rhs.grade
  || (grade == rhs.grade && name < rhs.name);
 }
 
 friend void operator << (ostream& output, const Student& s){
  output << s.name << " " << s.grade << endl;
 }
};

int main()
{
 vector<Student> vec;
 
 vec.emplace_back("Jack", 20);
 vec.emplace_back("John", 30);
 vec.emplace_back("Amy", 20);
 vec.emplace_back("Bill", 90);
 
 cout << "Before:" << endl;
 for(auto& s : vec){
  cout << s;
 }
 
 sort(begin(vec),end(vec));
 
 cout << endl << "After:" << endl;
 for(auto& s : vec){
  cout << s;
 }
 
 return 0;
}

bool cmp(const Student& lhs, const Student& rhs){
 return lhs.grade < rhs.grade
 || (lhs.grade == rhs.grade && lhs.name < rhs.name);
}

struct Compare{
 bool operator()(const Student& lhs, const Student& rhs){
  return lhs.grade < rhs.grade
  || (lhs.grade == rhs.grade && lhs.name < rhs.name);
 }
};

sort(begin(vec), end(vec), [](const Student& lhs, const Student& rhs) {
				return lhs.grade < rhs.grade 
				 || (lhs.grade == rhs.grade && lhs.name < rhs.name); });

#include "stdafx.h"
#include<iostream>
using namespace std;
class DescendNUM
{
public:
	DescendNUM(int x){ n = x;}//：构造函数，用参数x初始化n。
void decompose ();//：将n的各位数分解到a数组。
void dsort();//：将a数组排成降序。
void show();//：显示元素及其降序数。
private:
	int n;//：存放5位数的整数。
 int a[5];//：存放其元素的降序排列值。
};
 
void DescendNUM::decompose ()
{
	int i=0;
	while(n!=0)
	{
		a[i++] = n%10;
		n = n/10;
	}
}
void DescendNUM::dsort()
{
	int j,i,t;
	int num=a[0];
	for(i=0;i<4;i++)
	for(j=0;j<5;j++)
	{
		if(a[j+1]>a[j])
		{
   t=a[j+1];
		 a[j+1]=a[j];
		 a[j] = t;
		}
	}
}
void DescendNUM::show()
{
	int i;
	for(i=0;i<5;i++)
	{
		cout<<a[i];
	}
	cout<<endl;
}
int main()
{
	DescendNUM num(82319);
	num.decompose ();
	num.dsort();
	num.show();
	return 0;
}