石頭，紙張，剪刀，奇數輸出

Question

對於我的課堂項目，我們將制作一個“石頭，剪刀，剪刀布”游戲，使用一個功能來顯示菜單並驗證輸入，並使用一個功能來確定誰贏了。 當我繞過第一個函數時，我的代碼將編譯並正常運行。 但是，當我同時使用功能和I輸入1 ， 2 ，或3對我的選擇，它給了我-4195200作為值。

有什么幫助嗎？ 這是我的代碼：

// This project will be a game of Rock, Paper, Scissors

#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;

// Function Prototypes
int choices();
int userselect (int, int);

int main()
{

        //Variables and Seed
        int selection;
        char again;
        unsigned seed = time(0);
        srand(seed);
        int compselect = (rand()%3)+1;

        //Constants for the menu choices
        const int ROCK = 1,
                  PAPER = 2,
                  SCISSORS = 3;

        do
        {
                //Display the menu choices and validate
                choices();

                cout << "You picked " << selection << endl;
                cout << "The computer picked " << compselect << endl;

                //Display the results
                userselect(selection, compselect);

                //Replay loop
                cout << "Do you want to play again? (Y/N)";
                cin >> again;
        }
        while (again == 'Y' || again == 'y');
        return 0;
}

//***********************************************************
// This function will display the menu choices and validate *
//***********************************************************

int choices()
{
        int selection;

        cout << "********************************\n";
        cout << "*   Please Select A Choice     *\n";
        cout << "*          1 - Rock            *\n";
        cout << "*          2 - Paper           *\n";
        cout << "*          3 - Scissors        *\n";
        cout << "********************************\n";
        cin >> selection;

        //Validate the selection
        while (selection < 1 || selection > 3)
        {
                cout << "ERROR: Enter a valid choice.";
                cin >> selection;
        }

        return selection;
}

//***********************************************************
// This function will display the menu choices and validate *
//***********************************************************

int userselect (int num1, int num2)
{
         // If user enters Rock
        if (num1 == 1)
        {
                if (num2 == 1)
                {
                        cout << "You picked Rock \n";
                        cout << "The computer picked Rock \n";
                        cout << " TIE! \n";
                }
                else if (num2 == 2)
                {
                        cout << "You picked Rock \n";
                        cout << "The computer picked Paper \n";
                        cout << "Paper beats Rock. YOU LOSE! \n";
                }
                else if (num2 == 3)
                {
                        cout << "You picked Rock \n";
                        cout << "The computer picked Scissors \n";
                        cout << " Rock beats Scissors. YOU WIN! \n";
                }
        }

        // If user enters Paper
        if (num1 == 2)
        {
                if (num2 == 1)
                {
                        cout << "You picked Paper \n";
                        cout << "The computer picked Rock \n";
                        cout << " Paper beats Rock. YOU WIN! \n";
                }
                else if (num2 == 2)
                {
                        cout << "You picked Paper \n";
                        cout << "The computer picked Paper \n";
                        cout << " TIE! \n";
                }
                else if (num2 == 3)
                {
                        cout << "You picked Paper \n";
                        cout << "The computer picked Scissors \n";
                        cout << " Scissors beats Paper. YOU LOSE! \n";
                }
}

        // If user enters Scissors
        if (num1 == 3)
        {
                if (num2 == 1)
                {
                        cout << "You picked Scissors \n";
                        cout << "The computer picked Rock \n";
                        cout << " Rock beats Scissors. YOU LOSE! \n";
                }
                else if (num2 == 2)
                {
                        cout << "You picked Scissors \n";
                        cout << "The computer picked Paper \n";
                        cout << "Scissors beat Paper. YOU WIN! \n";
                }
                else if (num2 == 3)
                {
                        cout << "You picked Scissors \n";
                        cout << "The computer picked Scissors \n";
                        cout << " TIE! \n";
                }
        }
}

Answer 1

您沒有處理仍在cin輸入流中的換行符，也沒有對cin >> selection進行任何錯誤檢查，因此cin >> selection失敗。 因為失敗，所以selection沒有任何新值，並且由於沒有初始化，因此得到的是垃圾編號-4195200 。

你會看到這一點，如果你想進行一些錯誤檢查，或允許的錯誤檢查，你那種已經在你的while循環通過初始化做的工作selection ，以0 ：

int selection = 0;

您還沒有完全將調用choices()的結果存儲在main() 。 請記住， choices()的變量selection是局部變量，並且與main()的變量selection ，在此代碼中，您永遠不會為其分配值：

selection = choices();

Answer 2

給selection = choices()而不是choices()

Answer 3

您在函數choices();定義selection choices(); 作為局部變量，但在main()輸出全局selection 。

更換

choices();

同

selection = choices();