ç循环使用Y / N选项开关。选择N不关闭程序 [英] C Looping a switch using Y/N options. Choosing N doesn't close the program

问题描述

我只开始编码C.（这里的新生，没有经验，只有基本的HTML）
出于某种原因，每当我选择的选项'N'，它只是创建一个新的行。

在我的第二个 scanf函数每当我改变我的'％s'的，结果被更改。
当我使用，％D，输入一个数字，它不断地进入后选择1-4之间的一个数。如果我使用％C，输入号码后，就会直接跳到循环。帮助？

 的#include＆LT;＆stdio.h中GT;
诠释的main（）
{
    INT N，确定= 0;
    字符输入;
    而（OK == 0）
    {
          的printf（请选择1-4 \\ n之间的数字）;
          scanf函数（％d个，＆安培; N）;
          开关（N）
          {
                 情况1：
                      的printf（你选择了1号）;
                      打破;
                 案例2：
                      的printf（你选择了2号）;
                      打破;
                 案例3：
                      的printf（你选择了3号）;
                      打破;
                 情况4：
                      的printf（你选择了4号）;
                      打破;
                 默认：
                         的printf（你选择了一个无效的号码）;
          }
          的printf（\\ nInput试（Y / N）\\ n吗？）;
          scanf函数（％S，＆安培;输入）;
          如果（输入=='N'||输入=='N'）
          【OK ++;}
          否则，如果（输入=='Y'||输入=='Y'）
          {printf的（\\ n）;}
    } 的getchar（）;
 的getchar（）;
}
 

解决方案

改变

  scanf函数（％S，＆安培;输入）;
 

到

  scanf函数（％C，＆安培;输入）;
 

和摆脱中的getchar（）■在年底。这将作为你想要的。 ％C 说明读取一个char字符，但它不忽略空格字符。把空间到scanf函数的格式将处理空格和读取第一个非空格字符。为了更清楚，看什么人说页关于％C 格式说明：

  

（...）的前导空格通常的跳跃是pssed燮$ P $。跳过
  白空间的第一部分，格式使用一个明确的空间。
  结果

不过，如果你真的学习C ++，坚持与CIN / COUT，而不是scanf函数/ printf的的。

下面的程序将如何看就像如果你将取代的printf / scanf函数与CIN / COUT。如果你这样做previously，你不会有那样的麻烦。

 的#include＆LT;＆iostream的GT;使用命名空间std;诠释的main（）
{
    INT N，确定= 0;
    字符输入;
    而（OK！）
    {
        COUT＆LT;＆LT; 选择1-4 \\ n之间的数字;
        CIN＆GT;＆GT; N;        开关（N）
        {
            情况1：
                COUT＆LT;＆LT; 您已选择号码1;
                打破;
            案例2：
                COUT＆LT;＆LT; 您已选择号码2;
                打破;
            案例3：
                COUT＆LT;＆LT; 您已选择3号;
                打破;
            情况4：
                COUT＆LT;＆LT; 你选择了4号
                打破;
            默认：
                COUT＆LT;＆LT; 你选择了一个无效号码;
        }
        COUT＆LT;＆LT; ？\\ nInput试（Y / N）\\ n;
        CIN＆GT;＆GT;输入;        如果（输入=='N'||输入=='N'）
        {
            OK ++;
        }
        否则，如果（输入=='Y'||输入=='Y'）
        {
            COUT＆LT;＆LT; \\ n;
        }
    }    返回0;
}
 

I've only started coding C. (freshman here, no experience, only basic html) For some reason, whenever I choose the option 'N', it just creates a new line.

At my second scanf whenever I change my '%s', the result changes. When I use, "%d",after entering a number, it continuously enter "Choose a number between 1-4". If I use "%c",after entering a number, it will skip directly to the loop. Help?

#include <stdio.h>
int main()
{
    int n, ok = 0;
    char input;
    while (ok == 0)
    {
          printf("Choose a number between 1-4\n");
          scanf("%d", &n);
          switch (n)
          {
                 case 1:
                      printf("You've chosen number 1");
                      break;
                 case 2:
                      printf("You've chosen number 2");
                      break;
                 case 3:
                      printf("You've chosen number 3");
                      break;
                 case 4:
                      printf("You've chosen number 4");
                      break;
                 default:
                         printf("You have chosen an invalid number");
          }
          printf("\nInput again? (Y/N)\n");
          scanf("%s", &input);
          if (input=='n'||input=='N')
          {ok++;}
          else if (input=='Y'||input=='y')
          {printf("\n");}


    }

 getchar();
 getchar();   
}

解决方案

change

scanf("%s", &input);

to

scanf(" %c", &input);

and get rid of getchar()s at the end. It will work as you wanted. %c specifier reads a char character, but it does not omit whitespace characters. Putting space onto scanf's format will deal with whitespaces and read first non-whitespace char. To be more clear, see what man page says about %c format specifier:

(...) The usual skip of leading white space is suppressed. To skip white space first, use an explicit space in the format.

However, if you are really learning C++, stick with cin/cout, rather than scanf/printf's.

Here's how your program would look like if you would replace printf/scanf with cin/cout. If you've done that previously, you wouldn't had that kind of trouble.

#include <iostream>

using namespace std;

int main()
{
    int n, ok = 0;
    char input;
    while (!ok)
    {
        cout << "Choose a number between 1-4\n";
        cin >> n;

        switch (n)
        {
            case 1:
                cout << "You've chosen number 1";
                break;
            case 2:
                cout << "You've chosen number 2";
                break;
            case 3:
                cout << "You've chosen number 3";
                break;
            case 4:
                cout << "You've chosen number 4";
                break;
            default:
                cout << "You have chosen an invalid number";
        }
        cout << "\nInput again? (Y/N)\n";
        cin >> input;

        if (input=='n' || input=='N')
        {
            ok++;
        }
        else if (input=='Y' || input=='y')
        {
            cout << "\n";
        }
    }

    return 0;
}

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