c++ - 如何在同一个 while 循环中评估大于和小于的数字？

Question

// DiceRollProject.cpp : Defines the entry point for the console     application.
//

#include "stdafx.h"
#include <iostream>
#include <time.h>

using namespace std;

int diceRoll(int max);  // function definition
int getValidInteger();// function definition

int main() {

    srand(time(0)); // seed the random number generator

    int exitProgram = 0;
    int guess, rollValue;
    int maxRollValue = 6;
    cout << "Hello! Let's play a dice game. Let me do the first roll for you.\n" << endl;
    rollValue = diceRoll(maxRollValue);
    cout << "In this roll, you got: " << rollValue << "\n" << endl;

    do {
        rollValue = diceRoll(maxRollValue);


        cout << "What's your guess for the next roll? Enter an integer between 1 and " << maxRollValue << ": ";
        guess = getValidInteger();
        // TODO: Validate input

        if (guess > rollValue)
        {
            cout << "The guess was too high!";

        }

        if (guess < rollValue)
        {
            cout << "The guess was too low!";

        }

        if (guess == rollValue)
        {
            cout << "You guessed correctly, congrats!";

        }

        cout << "In this roll, you got: " << rollValue << "\n" << endl;
        // TODO: Evaluate result


        cout << "Enter 1 to exit or any other integer to continue rolling ";
        exitProgram = getValidInteger();
        cout << "\n";
        if (exitProgram == 1)
        {
            cout << "Sorry to see you go. Have a wonderful day!\n" << endl;
        }

    } while (exitProgram != 1);

    return 0;
}

// Roll the die
int diceRoll(int max) {
    int rollValue;

    rollValue = (rand() % max) + 1;

    return rollValue;
}


// Check if user entered an integer
int getValidInteger() {
    int userInput;

    cin >> userInput;

    while (userInput < 1)  {

        if (userInput < 1)
        {
            cout << "Please enter a number greater than or equal to 1\n";
        }

        if (userInput > 6)
        {
            cout << "Please enter a number less than or equal to 6\n";
        }

    }


    if (cin.fail()) {
        cin.clear();
        cin.ignore();
        cout << "Please enter an Integer only ";
        cin >> userInput;
        cout << "\n";
    }

    return userInput;
}

我有一个掷骰子猜谜游戏，我正在尝试评估用户输入，以确保他们不能输入小于 1 和大于 6 的数字，不幸的是，仅使用我的 if 语句，他们可以仍然输入这些数字，虽然显示输入无效的字符串，但我想做一个 while 循环，不断要求他们输入等于或大于 1 且等于和小于 6 的有效数字，如果用户保持输入不正确的数字，while 循环将不断询问他们输入有效数字，直到他们输入一个数字，然后程序将正常运行。

Answer 1

首先，在 while 循环中有死代码。

while (userInput < 1)  {

    if (userInput < 1)
    {
        cout << "Please enter a number greater than or equal to 1\n";
    }

    if (userInput > 6)
    {
        cout << "Please enter a number less than or equal to 6\n";
    }

}

在循环体内，第一个 if 始终为真，第二个始终为假。当用户写入无效输入时，您应该进入循环。这发生在 (userInput < 1 or userInput > 6)

在 while 的条件求值后，你应该要求用户写输入

do  {
    cout << "Please enter an Integer only ";
    cin >> userInput;
    if (userInput < 1)
    {
        cout << "Please enter a number greater than or equal to 1\n";
    }

    if (userInput > 6)
    {
        cout << "Please enter a number less than or equal to 6\n";
    }

}while(userInput < 1 || userInput > 6);