unordered_map

#include <iostream>
#include <string>
#include <unordered_map>

using namespace std;

int main() {
    // 创建一个unordered_map，键类型为string，值类型为int
    unordered_map<string, int> map;

    // 插入数据
    map["apple"] = 5;
    map["banana"] = 8;
    map["cherry"] = 3;

    // 访问数据
    cout << "apple has value: " << map["apple"] << endl;

    // 检查键是否存在并访问
    string key = "banana";
    if (map.find(key) != map.end()) {
        cout << key << " exists with value: " << map[key] << endl;
    } else {
        cout << key << " does not exist." << endl;
    }

    // 遍历unordered_map中的所有键值对
    cout << "All items in the unordered_map:" << endl;
    for (const auto &pair : map) {
        cout << pair.first << " has value: " << pair.second << endl;
    }

    // 删除一个元素
    map.erase("cherry");

    // 再次遍历以确认删除
    cout << "After erasing 'cherry':" << endl;
    for (const auto &pair : map) {
        cout << pair.first << " has value: " << pair.second << endl;
    }

    return 0;
}