本篇学习unordered_set的删除操作，具体的函数如下

#include <unordered_set>
#include <string>
#include <time.h>
#include <iostream>

using namespace std;


void changeOperator()
{
    //1.clear清除内容
    unordered_set<int> set1 = {1, 7, 3, 4, 2};
    cout << "set1 clear before size = " << set1.size() << " empty = " << set1.empty() << endl;
    set1.clear();
    cout << "set1 clear after size  = " << set1.size() << " empty = " << set1.empty() << endl;
    //2.erase擦除元素
    unordered_set<int> set2 = {10, 70, 30, 40, 20};
    cout << "set2 erase before size = " << set2.size() << "\t";
    for(auto val: set2)
    {
        cout << val << "\t";
    }
    set2.erase(13);//参数key
    set2.erase(30);//参数key
    cout << endl;
    cout << "set2 erase after  size = " << set2.size() << "\t";
    for(auto val: set2)
    {
        cout << val << "\t";
    }
    cout << endl;
    //3.swap交换内容
    unordered_set<int> set3 = {11, 71, 31, 41, 21};
    unordered_set<int> set4 = {12, 72, 32, 42, 22};
    cout << "set3 swap before size = " << set3.size() << "\t";
    for(auto val: set3)
    {
        cout << val << "\t";
    }
    cout << endl;
    cout << "set4 swap before size = " << set4.size() << "\t";
    for(auto val: set4)
    {
        cout << val << "\t";
    }
    cout << endl;
    set3.swap(set4);
    cout << "set3 swap after  size = " << set3.size() << "\t";
    for(auto val: set3)
    {
        cout << val << "\t";
    }
    cout << endl;
    cout << "set4 swap after  size = " << set4.size() << "\t";
    for(auto val: set4)
    {
        cout << val << "\t";
    }
    cout << endl;
    //4.extract从另一容器释出结点   C++17 提取
    unordered_set<int> set5 = {13, 73, 33, 43, 23};
    unordered_set<int> set6 = {56, 73};
    cout << "set5 extract before size = " << set5.size() << "\t";
    for(auto val: set5)
    {
        cout << val << "\t";
    }
    cout << endl;

    auto nh = set5.extract(33);//参数key
    nh.value() = 38;
    set6.insert(move(nh));//把一个节点移动另一个容器中
    cout << "set5 extract after  size = " << set5.size() << "\t";
    for(auto val: set5)
    {
        cout << val << "\t";
    }
    cout << endl;
    cout << "set6 extract after  size = " << set6.size() << "\t";
    for(auto val: set6)
    {
        cout << val << "\t";
    }
    cout << endl;
    //5.merge从另一容器接合结点   C++17
    unordered_set<int> set7 = {14, 74, 35, 47, 25};
    unordered_set<int> set8 = {12, 71, 35, 42, 25};
    cout << "set7 merge before size = " << set7.size() << "\t";
    for(auto val: set7)
    {
        cout << val << "\t";
    }
    cout << endl;
    cout << "set8 merge before size = " << set8.size() << "\t";
    for(auto val: set8)
    {
        cout << val << "\t";
    }
    cout << endl;
    set7.merge(set8);//如果有相同的值不会合并
    cout << "set7 merge after  size = " << set7.size() << "\t";
    for(auto val: set7)
    {
        cout << val << "\t";
    }
    cout << endl;
    cout << "set8 merge after  size = " << set8.size() << "\t";
    for(auto val: set8)
    {
        cout << val << "\t";
    }
    cout << endl;
}

int main()
{
    changeOperator();

    cout << "Hello, world!" << endl;
    return 0;
}

运行结果：

参考：

https://zh.cppreference.com/w/cpp/container/unordered_set