Question

我正在创建一个程序，它将获取n个项目的列表，然后消除每个第三个项目，直到只剩下1个项目。我收到一个错误，我的代码访问不存在的列表项。我知道我可以使用整数计数器修改它，但我更愿意找到问题的根源

int main()
{
    double suitors=0;
    int checker=0;
    int temp=0;
    do
    {
        cout << "How many suitors are there, min of 4 \n";
        cin >> suitors ;
        checker=suitors;
        if (cin.fail()||checker!=suitors||suitors<4)
        {
            cout << "You have entered an invalid input.\n";
            cin.clear();
            cin.ignore(100, '\n');
            suitors=-1;
        }
    }
    while (checker!=suitors||suitors<4);
    list<int> men;  

    for (int j=1; j<=suitors; j++)
    {
        men.push_back(j);
    }
    list<int>::iterator i;
    i=men.begin();

    for (int j=1; j<suitors;j++)
    {
        temp=0;
        while (temp<3)
        {
            temp=temp+1;
            if (temp==3)
            {
                cout << "Suitor #" << *i << " is eliminated \n";
                i=men.erase(i);
                break;
            }
            if (i!=men.end())
            {
                i++;
            }
            else //this is trying to reset the iterator to the start when it hits the end
            {
                i=men.begin();
            }
        }
    }
    i=men.begin();
    cout << "If there are " << suitors 
    << " then the winner will be suitors #" << *i << endl;
    return 0;
}

Answer 1

这部分是错误：

if (i!=men.end())
{
    i++;
}
else //this is trying to reset the iterator to the start when it hits the end
{
    i=men.begin();
}

如果i指向列表的最后一项，那么它将采用i != men.end()路由，执行++i，然后在下一次循环中执行i == men.end()

正确的代码是：

if(i == men.end())
    i = men.begin();
if(++i == men.end())
    i = men.begin();

C ++循环列表错误

1 个答案: