每次输入都要从文件中先加载数据到数组中，然后再把更新的数据添加进数组中，最后再写入文件 。

代码中文件路径填自己电脑的路径

#include<iostream>
#include<fstream>
#include<string>
#include<vector>
#include<algorithm>
#include<sstream>
using namespace std;

struct Player 
{
    string name;
    int score;
};

bool cmp(const Player& player1, const Player& player2)
{
    return player1.score > player2.score;
}

void updateRankings(const Player& newPlayer, vector<Player>& rankings, int maxPlayers) 
{
    rankings.push_back(newPlayer);
    sort(rankings.begin(), rankings.end(), cmp);
    if (rankings.size() > maxPlayers)
    {
        rankings.pop_back();
    }
}

void displayRankings(const vector<Player>& rankings)
{
    cout << "名次\t昵称\t积分\n";
    for (int i = 0; i < rankings.size(); ++i)
    {
        cout << i + 1 << "\t" << rankings[i].name << "\t" << rankings[i].score << "\n";
    }
}

void saveRankingsToFile(const vector<Player>& rankings, const string& filename) {
    ofstream file(filename);
    if (file.is_open()) 
    {
        for (int i = 0; i < rankings.size(); ++i)
        {
            file << rankings[i].name << " \t" << rankings[i].score << "\n";
        }
        file.close();
    }

    else
    {
        cout << "打开文件失败!";
    }
}

void loadRankingsFromFile(vector<Player>& rankings, const string& filename)
{
    ifstream file(filename);
    if (file.is_open()) 
    {
        string buffer;
        while (getline(file, buffer))
        {
            stringstream ss(buffer);
            string name;
            int score;
            ss >> name >> score;
            rankings.push_back({ name, score });
        }
        file.close();
    }

    else
    {
        cout << "打开文件失败!";
    }
}

int main()
{
    vector<Player> rankings;
    int maxPlayers = 10, score;
    string name;
    loadRankingsFromFile(rankings, R"(C:\\文件流\\zy.txt)");
    cin >> name >> score;
    Player newPlayer{ name, score };
    updateRankings(newPlayer, rankings, maxPlayers);
    displayRankings(rankings);
    saveRankingsToFile(rankings, R"(C:\\文件流\\zy.txt)");
    return 0;
}