C++循环问题：程序无法显示最终提示与循环逻辑异常求助

Hey there! Let's fix up your arithmetic game step by step. I see a few key issues with the loop logic and variable handling that are causing the "play again" prompt to not show up correctly. Let's break this down and get it working right.

• Your "play again" prompt was trapped inside a while (guess != num3) loop, which only runs if the user answers wrong. If they get the question right on the first try, this code never executes—so the prompt never appears.
• Variables Y and Q were defined as int types, but you need to accept character inputs like 'Y' or 'Q'. This type mismatch made your input checks completely ineffective.
• srand(time(0)) was placed inside the main loop, resetting the random seed every iteration. Since time(0) updates once per second, this resulted in nearly identical random numbers each time.
• There was a bug in the subtraction logic: num3 = num1 + num2 should be num3 = num1 - num2, which broke the correctness check for subtraction problems.
• The operation selection error handling only retried once—if the user messed up again, the program would proceed with invalid input.

#include <iostream>
#include <cstdio>
#include <time.h>
#include <stdlib.h>
using namespace std;

int main() {
    // Initialize random seed ONCE, outside the main loop
    srand(time(0));

    while (true) {
        // Generate two random single-digit integers (0-9)
        int num1 = rand() % 10;
        int num2 = rand() % 10;
        int operation, num3, guess;
        // Use char type for play input to handle 'Y'/'Q'
        char play;

        // Ensure num1 >= num2 to avoid negative subtraction results
        if (num1 < num2) {
            int temp = num1;
            num1 = num2;
            num2 = temp;
        }

        // Loop until user enters a valid operation (1/2/3)
        cout << "Choose an operation." << endl;
        cout << "Enter 1 to add, 2 to subtract, or 3 to multiply: " << endl;
        cin >> operation;
        while (operation > 3 || operation < 1) {
            cout << "Your operation choice isn't valid! Please try again, using 1, 2, or 3." << endl;
            cin >> operation;
        }

        // Handle addition
        if (operation == 1) {
            cout << "You chose addition." << endl;
            num3 = num1 + num2;
            cout << "What is " << num1 << " + " << num2 << " ?: " << endl;
            cin >> guess;
            // Loop until user answers correctly
            while (guess != num3) {
                cout << "That is incorrect. Please try again." << endl;
                cout << "What is " << num1 << " + " << num2 << " ?: " << endl;
                cin >> guess;
            }
            cout << "That is correct!" << endl << endl;
        }
        // Handle subtraction (fixed the num3 calculation bug)
        else if (operation == 2) {
            cout << "You chose subtraction." << endl;
            num3 = num1 - num2;
            cout << "What is " << num1 << " - " << num2 << " ?: " << endl;
            cin >> guess;
            while (guess != num3) {
                cout << "That is incorrect. Please try again." << endl;
                cout << "What is " << num1 << " - " << num2 << " ?: " << endl;
                cin >> guess;
            }
            cout << "That is correct!" << endl << endl;
        }
        // Handle multiplication
        else if (operation == 3) {
            cout << "You chose multiplication." << endl;
            num3 = num1 * num2;
            cout << "What is " << num1 << " * " << num2 << " ?: " << endl;
            cin >> guess;
            while (guess != num3) {
                cout << "That is incorrect. Please try again." << endl;
                cout << "What is " << num1 << " * " << num2 << " ?: " << endl;
                cin >> guess;
            }
            cout << "That is correct!" << endl << endl;
        }

        // Show play again prompt AFTER every completed question
        cout << "Would you like to play again? Press Y for yes or Q for quit" << endl;
        cin >> play;
        // Loop until user enters a valid choice (Y/y/Q/q)
        while (play != 'Y' && play != 'y' && play != 'Q' && play != 'q') {
            cout << "That is not a valid choice. Please choose Y for yes or Q to quit." << endl;
            cin >> play;
        }

        // Handle user's play again choice
        if (play == 'Q' || play == 'q') {
            cout << "Thank you for playing! See you next time!" << endl;
            break; // Exit the main loop to end the program
        } else {
            cout << "Thank you for playing! Let's play again!" << endl << endl;
            // No break here—main loop will restart with new numbers
        }
    }
    return 0;
}

• Random Seed Initialization: Moved srand(time(0)) outside the main loop so it only runs once. This ensures truly random numbers instead of nearly identical values each iteration.
• Valid Operation Check: Replaced single retry with a while loop to force the user to enter 1/2/3 before proceeding.
• Answer Retry Logic: Added while loops in each operation branch to let users keep trying until they get the answer right.
• Play Again Prompt Placement: Moved the prompt to after every completed question, so it always shows up regardless of whether the user answered correctly on the first try.
• Variable Type Fix: Changed play to a char type and used character constants ('Y', 'Q') for checks, fixing the type mismatch issue.
• Subtraction Bug Fix: Corrected num3 = num1 + num2 to num3 = num1 - num2 so subtraction answers are judged correctly.
• Case Insensitivity: Added checks for both uppercase and lowercase Y/Q to make the user experience more flexible.

内容的提问来源于stack exchange，提问作者amykp