【C++】STL中 sort、priority_queue 自定义 cmp 方法汇总（code c++）

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目录&索引

• 1 sort 函数中的 cmp
• • 1.1 重载小于运算符
  • 1.2 自定义 cmp 函数
  • 1.3 自定义仿函数
  • 1.4 自定义 lambda 表达式
  • 1.5 输出结果（逆序）
• 2 priority_queue 中的 cmp
• • 2.1 重载小于运算符
  • 2.2 自定义仿函数
  • 2.3 自定义 lambda 表达式
  • 2.4 输出结果（小顶堆）
• 3 结论

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1 sort 函数中的 cmp

1.1 重载小于运算符

sort 重载小于运算符，重载示例如下：

#include <iostream>
#include <algorithm>
using namespace std;

struct Student {
    string name;
    int num;
    int age;
    bool operator<(const Student &stu) const {
        return stu.age < this->age;
    }
};
 
int main() {
    Student stu[5] = {{"Zhang san", 1, 18}, {"Li Si", 2, 19}, {"Wang Er", 3, 20},
                      {"Ma Zi", 4, 21}, {"Lucy", 5, 17}};
    sort(stu, stu + 5);
    for (int i = 0; i < 5; ++i) {
        cout << stu[i].name << " is " << stu[i].age << endl;
    }
    return 0;
}

1.2 自定义 cmp 函数

sort 自定义 cmp 函数，示例如下：

#include <iostream>
#include <algorithm>
using namespace std;

struct Student {
    string name;
    int num;
    int age;
};

bool cmp(const Student &stu1, const Student &stu2) {
    return stu2.age < stu1.age;
}
 
int main() {
    Student stu[5] = {{"Zhang san", 1, 18}, {"Li Si", 2, 19}, {"Wang Er", 3, 20},
                      {"Ma Zi", 4, 21}, {"Lucy", 5, 17}};
    sort(stu, stu + 5, cmp);
    for (int i = 0; i < 5; ++i) {
        cout << stu[i].name << " is " << stu[i].age << endl;
    }
    return 0;
}

1.3 自定义仿函数

sort 自定义仿函数，示例如下：

#include <iostream>
#include <algorithm>
using namespace std;

struct Student {
    string name;
    int num;
    int age;
};

struct cmp {
    bool operator()(const Student &stu1, const Student &stu2) {
        return stu2.age < stu1.age;
    }
};

int main() {
    Student stu[5] = {{"Zhang san", 1, 18}, {"Li Si", 2, 19}, {"Wang Er", 3, 20},
                      {"Ma Zi", 4, 21}, {"Lucy", 5, 17}};
    sort(stu, stu + 5, cmp()); // cmp() 为匿名对象
    for (int i = 0; i < 5; ++i) {
        cout << stu[i].name << " is " << stu[i].age << endl;
    }
    return 0;
}

1.4 自定义 lambda 表达式

sort 自定义 lambda 表达式，示例如下：

#include <iostream>
#include <algorithm>
using namespace std;

struct Student {
    string name;
    int num;
    int age;
};

int main() {
    Student stu[5] = {{"Zhang san", 1, 18}, {"Li Si", 2, 19}, {"Wang Er", 3, 20},
                      {"Ma Zi", 4, 21}, {"Lucy", 5, 17}};
    sort(stu, stu + 5, 
         [](const Student &stu1, const Student &stu2) { return stu2.age < stu1.age; });
    for (int i = 0; i < 5; ++i) {
        cout << stu[i].name << " is " << stu[i].age << endl;
    }
    return 0;
}

1.5 输出结果（逆序）

年龄从大到小输出，结果如下：

Ma Zi is 21
Wang Er is 20
Li Si is 19
Zhang san is 18
Lucy is 17

---

2 priority_queue 中的 cmp

2.1 重载小于运算符

priority_queue 重载小于运算符，重载示例如下：

#include <iostream>
#include <queue>
using namespace std;

struct Student {
    string name;
    int num;
    int age;
    bool operator<(const Student &stu) const {
        return stu.age < this->age;
    }
};
 
int main() {
    Student stu[5] = {{"Zhang san", 1, 18}, {"Li Si", 2, 19}, {"Wang Er", 3, 20},
                      {"Ma Zi", 4, 21}, {"Lucy", 5, 17}};
    priority_queue<Student> q;
    for (int i = 0; i < 5; ++i) {
        q.push(stu[i]);
    }
    while (!q.empty()) {
        cout << q.top().name << " is " << q.top().age << endl;
        q.pop();
    }
    return 0;
}

2.2 自定义仿函数

priority_queue 自定义仿函数，示例如下：

#include <iostream>
#include <queue>
using namespace std;

struct Student {
    string name;
    int num;
    int age;
};

struct cmp {
    bool operator()(const Student &stu1, const Student &stu2) {
        return stu2.age < stu1.age;
    }
};
 
int main() {
    Student stu[5] = {{"Zhang san", 1, 18}, {"Li Si", 2, 19}, {"Wang Er", 3, 20},
                      {"Ma Zi", 4, 21}, {"Lucy", 5, 17}};
    priority_queue<Student, vector<Student>, cmp> q;
    for (int i = 0; i < 5; ++i) {
        q.push(stu[i]);
    }
    while (!q.empty()) {
        cout << q.top().name << " is " << q.top().age << endl;
        q.pop();
    }
    return 0;
}

2.3 自定义 lambda 表达式

priority_queue 自定义 lambda 表达式，示例如下：

#include <iostream>
#include <queue>
using namespace std;

struct Student {
    string name;
    int num;
    int age;
};

auto cmp = [](const Student &stu1, const Student &stu2) {
    return stu2.age < stu1.age;
};

int main() {
    Student stu[5] = {{"Zhang san", 1, 18}, {"Li Si", 2, 19}, {"Wang Er", 3, 20},
                      {"Ma Zi", 4, 21}, {"Lucy", 5, 17}};
    priority_queue<Student, vector<Student>, decltype(cmp)> q(cmp);
    for (int i = 0; i < 5; ++i) {
        q.push(stu[i]);
    }
    while (!q.empty()) {
        cout << q.top().name << " is " << q.top().age << endl;
        q.pop();
    }
    return 0;
}

2.4 输出结果（小顶堆）

大顶堆改为小顶堆，年龄从小到大输出，结果如下：

Lucy is 17
Zhang san is 18
Li Si is 19
Wang Er is 20
Ma Zi is 21

3 结论

sort 的 cmp 函数，priority_queue 的 cmp 类型。

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本文标签： 自定义方法sortstlpriorityqueue