sort与priority_queue的重载运算符，以及字符数组形参的传递

前提：

学生结构体

实现自定义顺序输出

typedef struct student {
    int grade;
    char name[100];
    int year;
} student;

①重写构造函数-字符数组形参的传递

char* name：可写的

const char* name：只读的

区别：strcpy与strcmp

student(int grade, const char* name,int year) {
        this->grade=grade;
        strcpy(this->name,name);
        this->year=year;
}

②重载运算符

类内重载

1，只能有一个参数,注意const和&

2，参数括号后面加一个const

typedef struct student {
    int grade;
    char name[100];
    int year;
    
    bool operator< (const student &b) const{
        if(this->grade==b.grade) {
            int x=strcmp(this->name,b.name);
            if(x==0) return this->year<b.year;
            else return x>0;
        } else 
            return this->grade>b.grade;
        
    }

} student;

类外重载

1，两个参数，注意const和&

2，友元函数friend

typedef struct student {
    int grade;
    char name[100];
    int year;
    friend bool operator< (const student &a, const student &b);
} student;

bool operator< (const student &a, const student &b) {
    if(a.grade==b.grade) {
        int x=strcmp(a.name,b.name);
        if(x==0) return a.year<b.year;
        else return x>0;
    } else {
        return a.grade>b.grade;
    }
}

③priority_queue中的用法

#include <bits/stdc++.h>
using namespace std;

typedef struct student {
    int grade;
    char name[100];
    int year;
    student(int grade, const char* name,int year){
        this->grade=grade;
        strcpy(this->name,name);
        this->year=year;
    }
} student;

bool operator< (const student &a, const student &b) {
    if(a.grade==b.grade) {
        int x=strcmp(a.name,b.name);
        if(x==0) return a.year<b.year;//year小在后
        else return x>0;//name大在后
    } else {
        return a.grade>b.grade;//grade大则返回true，则<，则优先级低，则在后
    }
}
 
int main() {
    priority_queue<student> q;
    q.push(student(10,"ab",4));
    q.push(student(10,"ac",7));
    q.push(student(10,"ac",2));
    q.push(student(11,"xx",4));
    
    while(!q.empty()){
        student stu=q.top();
        cout<<stu.grade<<" "<<stu.name<<" "<<stu.year<<endl;
        q.pop();
    }
    
}

输出

10 ab 4
10 ac 7
10 ac 2
11 xx 4

④sort的用法

#include <bits/stdc++.h>
using namespace std;

typedef struct student {
    int grade;
    char name[100];
    int year;
    student(int grade, const char* name,int year) {
        this->grade=grade;
        strcpy(this->name,name);
        this->year=year;
    }
    bool operator< (const student &b) const{
        if(this->grade==b.grade) {
            int x=strcmp(this->name,b.name);
            if(x==0) return this->year<b.year;//year小在前
            else return x>0;//name大在前
        } else {
            return this->grade>b.grade;//grade大在前
        }
    }

} student;

int main() {
    student stu[4]={{10,"ab",4},{10,"ac",7},{10,"ac",2},{11,"xx",4}};
    sort(stu,stu+4);
    for(int i=0;i<4;i++){
        cout<<stu[i].grade<<" "<<stu[i].name<<" "<<stu[i].year<<endl;
    }
        
    
    
}

输出

11 xx 4
10 ac 2
10 ac 7
10 ab 4

结论：sort与priority_queue相反