C++ for 循环在输入后结束

Question

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

struct Student {
    string name;
    string hometown;
    int age;
    int games;
    int* hours = new int [games];
};

int main(){
    int players;
    Student* s = new Student [players];

    cout << "How many esports players are there at TTU who major in csc?\n";
    cin >> players;
    cout << "\nPlease enter in information about each player: \n\n";

    for(int i = 0; i < players; i++){
        cout << "PLAYER " << (i + 1) << ":\n";
        cout << "\tNAME:\t";
        getline(cin >> ws, s[i].name);
        cout << "\tHOMETOWN:\t";
        getline(cin >> ws, s[i].hometown);
        cout << "\tAGE:\t";
        cin >> s[i].age;
        cout << "\tHOW MANY GAMES DOES " << s[i].name << " PLAY?\t";
        cin >> s[i].games;
            for(int j = 0; j < s[i].games; j++){
                cout << "NUMBER OF HOURS " << s[i].name << "PLAYED GAME"  << (j + 1) << "\t";
                cin >> s[i].hours[j];
            }
    } 

    return 0;
}

由于某种原因，for 循环在询问年龄后结束。我尝试了多个输入，它做同样的事情。我是 C++ 新手。有谁知道为什么？感谢您的宝贵时间

Answer 1

您没有正确处理数组。您正在使用未初始化的变量来分配它们的大小：

• 在int games; int* hours = new int [games]; 中，games 未初始化。
• 在int players; Student* s = new Student [players]; 中，players 未初始化。

而且，即使你正确地分配了数组，你也会泄漏它们，因为当你用完它们时你并没有释放它们。

当你需要使用一个直到运行时才知道大小的数组时，你使用new[]是正确的，但是直到在你确定了大小之后，例如：

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

struct Student {
    string name;
    string hometown;
    int age = 0;
    int games = 0;
    int* hours = nullptr;
};

int main(){
    cout << "How many esports players are there at TTU who major in csc?\n";

    int players;
    cin >> players;

    Student *s = new Student[players];

    cout << "\nPlease enter in information about each player: \n\n";

    for(int i = 0; i < players; ++i){
        cout << "PLAYER " << (i + 1) << ":\n";
        cout << "\tNAME:\t";
        getline(cin >> ws, s[i].name);
        cout << "\tHOMETOWN:\t";
        getline(cin >> ws, s[i].hometown);
        cout << "\tAGE:\t";
        cin >> s[i].age;
        cout << "\tHOW MANY GAMES DOES " << s[i].name << " PLAY?\t";
        cin >> s[i].games;
        s[i].hours = new int[s[i].games];
        for(int j = 0; j < s[i].games; ++j){
            cout << "NUMBER OF HOURS " << s[i].name << " PLAYED GAME " << (j + 1) << "\t";
            cin >> s[i].hours[j];
        }
    }

   // use player info as neded...

    for(int i = 0; i < players; ++i){
        delete[] s[i].hours;
    }
    delete[] s;

    return 0;
}

话虽如此，您应该手动使用std::vector 而不是new[]/delete[]，例如：

#include <iostream>
#include <string>
#include <vector>
using namespace std;

struct Student {
    string name;
    string hometown;
    int age = 0;
    int games = 0;
    std::vector<int> hours;
};

int main(){
    cout << "How many esports players are there at TTU who major in csc?\n";

    int players;
    cin >> players;

    std::vector<Student> s(players);

    cout << "\nPlease enter in information about each player: \n\n";

    for(int i = 0; i < players; ++i){
        cout << "PLAYER " << (i + 1) << ":\n";
        cout << "\tNAME:\t";
        getline(cin >> ws, s[i].name);
        cout << "\tHOMETOWN:\t";
        getline(cin >> ws, s[i].hometown);
        cout << "\tAGE:\t";
        cin >> s[i].age;
        cout << "\tHOW MANY GAMES DOES " << s[i].name << " PLAY?\t";
        cin >> s[i].games;
        s[i].hours.resize(s[i].games);
        for(int j = 0; j < s[i].games; ++j){
            cout << "NUMBER OF HOURS " << s[i].name << " PLAYED GAME " << (j + 1) << "\t";
            cin >> s[i].hours[j];
        }
    } 

    // use player info as needed...

    return 0;
}