c++程序：用vector容器储存城市的历史人口信息，并可以进行添加，删除，排序，查找等功能

以下是一个使用vector容器储存城市历史人口信息的示例程序，程序中实现了添加、删除、排序和查找等功能：

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

struct City {
    string name;
    int population;

    bool operator<(const City &other) const {
        return name < other.name;
    }
};

void printCity(const City &city) {
    cout << "City name: " << city.name << ", population: " << city.population << endl;
}

void addCity(vector<City> &cities) {
    cout << "Enter city name: ";
    string name;
    getline(cin, name);

    cout << "Enter population: ";
    int population;
    cin >> population;

    cin.ignore(); // Ignore the newline character left in the input buffer after reading population

    City city = {name, population};
    cities.push_back(city);

    cout << "City added successfully!" << endl;
}

void deleteCity(vector<City> &cities) {
    cout << "Enter city name to delete: ";
    string name;
    getline(cin, name);

    auto it = find_if(cities.begin(), cities.end(), [&](const City &city) {
        return city.name == name;
    });

    if (it != cities.end()) {
        cities.erase(it);
        cout << "City deleted successfully!" << endl;
    } else {
        cout << "City not found!" << endl;
    }
}

void sortCities(vector<City> &cities) {
    sort(cities.begin(), cities.end());
    cout << "Cities sorted by name!" << endl;
}

void searchCity(vector<City> &cities) {
    cout << "Enter city name to search: ";
    string name;
    getline(cin, name);

    auto it = find_if(cities.begin(), cities.end(), [&](const City &city) {
        return city.name == name;
    });

    if (it != cities.end()) {
        printCity(*it);
    } else {
        cout << "City not found!" << endl;
    }
}

int main() {
    vector<City> cities;

    while (true) {
        cout << "Select an option:" << endl;
        cout << "1. Add city" << endl;
        cout << "2. Delete city" << endl;
        cout << "3. Sort cities by name" << endl;
        cout << "4. Search city" << endl;
        cout << "5. Exit" << endl;

        int option;
        cin >> option;

        cin.ignore(); // Ignore the newline character left in the input buffer after reading option

        switch (option) {
            case 1:
                addCity(cities);
                break;
            case 2:
                deleteCity(cities);
                break;
            case 3:
                sortCities(cities);
                break;
            case 4:
                searchCity(cities);
                break;
            case 5:
                cout << "Goodbye!" << endl;
                return 0;
            default:
                cout << "Invalid option! Please try again." << endl;
                break;
        }

        cout << endl;
    }

    return 0;
}

在程序中，我们定义了一个名为`City`的结构体，其中包含了城市的名称和人口。为了实现按照城市名称排序的功能，我们在结构体中重载了小于号运算符。

在`addCity`函数中，我们使用了`getline`函数来读取用户输入的字符串，并使用`cin.ignore`函数来忽略读取人口数后留在输入缓冲区中的换行符。在`deleteCity`和`searchCity`函数中，我们使用了`find_if`算法来查找城市。

在程序的主函数中，我们使用了一个无限循环来接受用户的操作选择，并根据用户的选择调用相应的函数。