c++ sort 和 priority_queue中的自定义排序

sort（）

声明

template <class RandomAccessIterator, class Compare>
  void sort (RandomAccessIterator first, RandomAccessIterator last, Compare comp);

示例

// sort algorithm example
#include <iostream>
#include <algorithm>
#include <vector>
#include <string>


using namespace std;

// 定义结构体
struct student
{
    int age;
    string name;
    student(int a, string s)
    {
        age = a;
        name = s;
    }
};


// 自定义比较函数
bool myfunction(int i, int j) {
    return (i < j);
}


//重载运算符 注意参数类型要求
bool operator<(const student s1, const student s2)
{
    if (s1.age == s2.age)
        return s1.name < s2.name;//年龄相同时，按姓名小到大排
    else
        return s1.age < s2.age; //从年龄小到大排序
}


// 声明比较类
struct cmp
{
    bool operator() (const student& s1, const student& s2)
    {
        if (s1.age == s2.age)
            return s1.name < s2.name;
        else  return s1.age < s2.age;
    }
}mycmp;

struct cmp2
{
    bool operator() (int a, int b)
    {
        return a < b;
    }
}mycmp2;


int main() {
    vector<int> vec = { 32,71,12,45,26,80,53,33 };


    // 使用默认比较器 (operator <):
    sort(vec.begin(), vec.end());        //12 26 32 33 45 53 71 80

    // 自定义比较函数（函数指针）
    sort(vec.begin() + 4, vec.end(), myfunction);        // 12 32 45 71(26 33 53 80)

    // 重载比较运算符
    student s1(10, "wangwu");
    student s2(10, "lisi");
    student s3(12, "zhangsan");
    vector<student> s = { s1, s2, s3 };
    //sort(s.begin(), s.end());        //s2 s1 s3


    // 声明比较类
    // 注意二者写法的区别
    sort(s.begin(), s.end(), cmp());        //s2 s1 s3
    sort(s.begin(), s.end(), mycmp);        //s2 s1 s3

    sort(vec.begin(), vec.end(), cmp2());        //12 26 32 33 45 53 71 80
    sort(vec.begin(), vec.end(), mycmp2);        //12 26 32 33 45 53 71 80

    // 使用匿名函数
    sort(vec.begin(), vec.end(), [](int a, int b) {return a < b; });        //12 26 32 33 45 53 71 80

    system("pause");
    return 0;
}

 

 

priority_queue

声明

template <class T, class Container = vector<T>,
  class Compare = less<typename Container::value_type> > class priority_queue;

示例

#include<iostream>
#include<queue>
#include<vector>
#include <functional>

using namespace std;

template<typename T> void print_queue(T& q) {
    while (!q.empty()) {
        cout << q.top() << " ";
        q.pop();
    }
    cout << endl;;
}

// 声明比较类
struct comp
{
    bool operator()(int in1, int in2) const
    {
        return (in1>in2);
    }
};


int main()
{
    vector<int> v = { 1,3,5,7,9,2,4,6,8,10 };
    priority_queue<int> q1;
    for (auto c : v)
    {
        q1.push(c);
    }
    print_queue(q1);

    priority_queue<int, vector<int>, greater<int> > q2;
    for (auto c : v)
    {
        q2.push(c);
    }
    print_queue(q2);

    // 使用匿名函数
    auto cmp = [](int a, int b) { return a < b; };
    priority_queue<int, vector<int>, decltype(cmp)> q3(cmp);
    for (auto c : v)
    {
        q3.push(c);
    }
    print_queue(q3);

    int a = 4;

    // 声明比较类
    priority_queue<int, vector<int>, comp> q4;
    for (auto c : v)
    {
        q4.push(c);
    }
    print_queue(q4);


    cout << "\n" << endl;
    system("pause");
    return 0;
}