C++：提示需要多次输入数据才能继续

Question

我编写的以下程序提示用户输入一个数字 1 - 100。该程序从随机数生成器中预选了一个数字，用户必须猜测该数字。如果用户的猜测太高或太低，那么程序将通知用户，直到用户的猜测是正确的。我的程序运行良好，但是当提示输入数字时，在某些情况下我必须输入数字四次或更多次，程序才会提示我。有人可以告诉我或帮助我找出我的错误吗？

#include <iostream>
#include <ctime>//A user stated that using this piece of code would make a true randomization process.
#include <cstdlib>
using namespace std;

int main()//When inputing a number, sometimes the user has to input it more than once.
{
    int x;
    int ranNum;
    srand( time(0));

    ranNum = rand() % 100 + 1;

    cout << "Please input your guess for a random number between 1 - 100.\n";
    cin >> x;

    while (x > ranNum || x < ranNum)
    {
        {
            if (x > ranNum)
                cout << "Your input was greater than the system's generated random number. Please try again.\n";
            cin >> x;
            if (x > 100 || x < 1)
                cout << "Input invalid. Please input a number between 1 - 100.\n";
            cin >> x;
        }
        {
            if (x < ranNum)
                cout << "Your input was less than the system's generated random number. Please try again.\n";
            cin >> x;
            if (x > 100 || x < 1)
                cout << "Input invalid. Please input a number between 1 - 100.\n";
            cin >> x;
        }
        {
            if (x == ranNum)
                cout << "You guessed right!\n";
        }
    }

    return 0;
}

Answer 1

你的括号放错地方了。包含多行的 if 语句应采用

的形式

if (condition)
{
    code1
    code2
    code3
    ...
}

你拥有的是

{
    if condition
        code1
        code2
        code3
        ...
}

所以 code1 只会在条件为真时运行但 code2、code3 和其余的无论如何都会运行。缩进在 C++ 中没有任何意义。我们可以（请永远不要这样做）：

            if (condition)
    {
code1
code2
        code3
}

并且所有三行在 if 语句中都是运行。

您的代码更正后方括号位于正确的位置

while (x != ranNum)
{
    if (x > ranNum)
    {
        cout << "Your input was greater than the system's generated random number. Please try again.\n";
        cin >> x;
        if (x > 100 || x < 1)
        {
            cout << "Input invalid. Please input a number between 1 - 100.\n";
            cin >> x;
        }
    }
    if (x < ranNum)
    {
        cout << "Your input was less than the system's generated random number. Please try again.\n";
        cin >> x;
        if (x > 100 || x < 1)
        {
            cout << "Input invalid. Please input a number between 1 - 100.\n";
            cin >> x;
        }
    }
    if (x == ranNum)
        cout << "You guessed right!\n";
}

我也将 while (x > ranNum || x < ranNum) 更改为 while (x != ranNum) 因为我们只想运行循环而 x 不等于 ranNum

Answer 2

您没有正确使用 if 语句：

{
    if (x > ranNum)
        cout << "Your input was greater than the system's generated random number. Please try again.\n";
    cin >> x;
    if (x > 100 || x < 1)
        cout << "Input invalid. Please input a number between 1 - 100.\n";
    cin >> x;
}

上述两个if条件都不会影响任何东西，除了是否打印输出消息，并且周围的花括号也没有用。当条件代码由多条语句组成时，需要将其用大括号括起来：

{
    if (x > ranNum)
    {
        cout << "Your input was greater than the system's generated random number. Please try again.\n";
        cin >> x;
    }
    if (x > 100 || x < 1)
    {
        cout << "Input invalid. Please input a number between 1 - 100.\n";
        cin >> x;
    }
}

此外，复制读取输入和执行范围检查的代码也没有意义。以下内容对我来说更直接：

int main()
{
    int ranNum;
    srand( time(0));

    ranNum = rand() % 100 + 1;

    cout << "Please input your guess for a random number between 1 - 100.\n";
    cin >> x;

    int x;
    for (;;) // Endless loop
    {                  
        cin >> x;

        if (x > 100 || x < 1)
        {
            cout << "Input invalid. Please input a number between 1 - 100.\n";
            continue; // Jump to next iteration of the loop
        }                                             

        if (x == ranNum)                              
        {
            cout << "You guessed right!\n";
            break; // Leave the loop
        }

        if (x > ranNum)
            cout << "Your input was greater than the system's generated random number. Please try again.\n";
        else
            cout << "Your input was less than the system's generated random number. Please try again.\n";
    }

    return 0;
}

Answer 3

您的代码可能如下所示：

#include <iostream>
#include <ctime>//A user stated that using this piece of code would make a true randomization process.
#include <cstdlib>
using namespace std;

int main()//When inputing a number, sometimes the user has to input it more than once.
{
    int x;
int ranNum;
srand(time(0));

ranNum = rand() % 100 + 1;

cout << "Please input your guess for a random number between 1 - 100.\n";


while (x > ranNum || x < ranNum)
{
    cin >> x;
    if (x > ranNum && x<=100 & x>=1) cout << "Your input was greater than the system's generated random number. Please try again.\n";
    else if (x < ranNum && x<=100 & x>=1) cout << "Your input was smaller than the system's generated random number. Please try again.\n";
    else if (x>=100 || x<=1) cout << "Input invalid. Please input a number between 1 - 100.\n";

}
cout << "You guessed right!\n";

    return 0;
}

未来：

当你使用 while 循环时，它包含了 if 语句。使用得当。另外，尝试 nt 嵌套 if 语句，但改用逻辑运算符。

C++：提示需要多次输入数据才能继续

C++: Prompt Requires Data to be Inputted Multiple Times to Proceed

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random

cin