在以下 c 程序中，如果条件不起作用答案

【问题标题】：In the following c program if condition is not working在以下 c 程序中，如果条件不起作用
【发布时间】：2015-10-05 13:33:43
【问题描述】：

#include <stdio.h>
#include <conio.h>
#include <ctype.h>
#include <stdlib.h>
#include <time.h>

main()
{
    int iRandom;
    int iResponse;
    srand(time(0));

    iRandom = (rand() % 10) + 1;

    printf("\nGuess a number between 1 and 10: ");
    scanf("%c", &iResponse);

    if (isdigit(iResponse)) {

        iResponse = iResponse - '0';

        if (iResponse >=1 && iResponse <=10 ) {


            if (iResponse == iRandom) {
                printf("\nYou guessed right.\n");
            }
            else {
                printf("\nSorry, you guessed wrong.\n");
                printf("The correct guess was %d\n", iRandom);
            }
        }
        else {
            printf("You did not enter a digit between 1 and 10.");
        }

    }
    else {
        printf("\nYou did not enter a digit.\n");
    }

    getch();
    return 0;
}

如果 (iResponse >=1 && iResponse

【问题讨论】：

int iResponse; => char iResponse;
main() --> int main(void)

标签： c if-statement char

【解决方案1】：

问题出在这一行

 scanf("%c", &iResponse);

当您输入例如 47 作为输入时，它只需要 4 而不是 47 它只读取一个字符 '4' 。 “47”不是字符。因此，只要您输入某个数字，它就会始终进入该条件。但是，如果您尝试输入“a”作为输入，它会返回您

You did not enter a digit

您可以使用以下代码使其工作

#include <stdio.h>
#include <conio.h>
#include <ctype.h>
#include <stdlib.h>
#include <time.h>

main()
{
    int iRandom;
    int iResponse;
    srand(time(0));

    iRandom = (rand() % 10) + 1;

    printf("\nGuess a number between 1 and 10: ");
    scanf("%d", &iResponse);

    if (isdigit(iResponse+'0') || iResponse==10) {



        if (iResponse >=1 && iResponse <=10 ) {


            if (iResponse == iRandom) {
                printf("\nYou guessed right.\n");
            }
            else {
                printf("\nSorry, you guessed wrong.\n");
                printf("The correct guess was %d\n", iRandom);
            }
        }
        else {
            printf("You did not enter a digit between 1 and 10.");
        }

    }
    else {
        printf("\nYou did not enter a digit.\n");
    }

    getch();
    return 0;
}

【讨论】：

47 无法输入。提到输入应该在 1 到 10 之间。
如果 (iResponse >=1 && iResponse
@MIRMIX 你解释得对。一些天才对你和我投了反对票。

【解决方案2】：

为了对您的程序有一个好的方法，我认为您想检查用户输入以确保它是您所期望的。这意味着您需要检查输入是否仅包含数字。试试这个：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define TRUE 1
#define RANDOM 10

void clean_stdin(void){
    int c;
    while((c = getchar()) != 0 && c != '\n');
}

int inputCheck(void){
    int number;
    char c;

    do{
        printf("\tPlease type a Number: ");
        if (scanf("%d%c", &number, &c) == 0 || c != '\n'){
            printf("\nLetter[s] was Found in your Answear\n\n\n");
            clean_stdin();
        }else{
            break;
        }
    }while(TRUE);

    return number;
}

int main(void){
    int iResponse;
    int iRandom ;
    srand ( (unsigned int)time(NULL) );

    iRandom = (rand() % 10 + 1);
    iResponse = inputCheck();

    if(iRandom == iResponse){
        printf("\nYou guessed right.\n");
    }else{
        printf( "\nSorry, you guessed wrong.\n" );
        printf( "\n\t\t\tThe correct guess was %u\n", iRandom );
    }

    return(0);
}

你会得到：

  Please type a Number: 3r

Letter[s] was Found in your Answear


    Please type a Number: G7

Letter[s] was Found in your Answear


    Please type a Number: 6

Sorry, you guessed wrong.

            The correct guess was 4

  Please type a Number: 4

You guessed right.

通过这种方法，您可以告知用户他/她的输入。

如果你想告诉用户这个数字在 1 到 10 之间，你可以这样做：

    #include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define TRUE 1
#define MIN_RANDOM 1
#define Max_RANDOM 10

void clean_stdin(void){
    int c;
    while((c = getchar()) != 0 && c != '\n');
}

int inputCheck(int min, int max){
    int number;
    char c;

    do{
    printf("\tPlease type a Number::\t");
    if (scanf("%d%c", &number, &c) == 0 || c != '\n'){
        clean_stdin();
        printf("\nLetter[s] was Found in your Answear\n\n\n");
    }else if(number < min || number > max){
        printf("The number has to be wetween %d and %d\n\n",min, max);
    }else{
        break;
    }
    }while(TRUE);

    return number;
}

int main(void){
    int iResponse;
    int iRandom ;
    srand ( (unsigned int)time(NULL) );

    iRandom = (rand() % Max_RANDOM + MIN_RANDOM);
    iResponse = inputCheck(MIN_RANDOM,Max_RANDOM);

    if(iRandom == iResponse){
    printf("\nYou guessed right.\n");
    }else{
    printf( "\nSorry, you guessed wrong.\n" );
    printf( "\n\t\t\tThe correct guess was %u\n", iRandom );
    }

    return(0);
}

输出将是这样的：

  Please type a Number::  A1

Letter[s] was Found in your Answear


    Please type a Number::  1A

Letter[s] was Found in your Answear


    Please type a Number::  15
The number has to be wetween 1 and 10

    Please type a Number::  4

Sorry, you guessed wrong.

            The correct guess was 8

【讨论】：

【解决方案3】：

实际上，您将iResponse 声明为integer 变量，并在scanf 中将说明符写为%c，即字符。

scanf("%c", &iResponse);

改成-

scanf("%d", &iResponse);

【讨论】：

【解决方案4】：

我认为你的意思是以下

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <errno.h>

int main( void )
{
    char line[20];
    unsigned int iRandom;
    unsigned int iResponse;

    const unsigned int Base = 10;

    srand( ( unsigned int )time( NULL ) );

    iRandom = rand() % Base + 1;

    printf( "\nGuess a number between 1 and %u: ", Base );
    scanf( "%20s", line );

    errno = 0;
    iResponse = ( unsigned int )strtoul( line, NULL, Base );

    if ( !errno && iResponse >= 1 && iResponse <=10 ) 
    {
        if ( iResponse == iRandom ) 
        {
            puts( "\nYou guessed right." );
        }
        else 
        {
            puts( "\nSorry, you guessed wrong." );
            printf( "The correct guess was %u\n", iRandom );
        }
    }
    else 
    {
        puts( "\nYou did not enter a number" );
    }

    return 0;
}

程序输出可能如下所示

Guess a number between 1 and 10: A
You did not enter a number

Guess a number between 1 and 10: 4
Sorry, you guessed wrong.
The correct guess was 3

Guess a number between 1 and 10: 4
You guessed right.

至于你的代码，那么至少在这个语句中

scanf("%c", &iResponse);

您应该将"%c" 替换为" %c"（%c 之前的空白）。尽管即使在这种情况下，结果也将由实现定义。而且使用这种方法你将无法输入可接受的号码10。:)

【讨论】：

【解决方案5】：

改变

scanf("%c", &iResponse);

if (isdigit(iResponse)) {
    . . .

到

if (scanf("%d", &iResponse)) {
    . . .

工作代码将如下所示

#include <stdio.h>
#include <time.h>

int main() {
    srand(time(0));
    int iRandom = (rand() % 10) + 1, iResponse;
    printf("\nGuess a number between 1 and 10: ");
    if (scanf("%d", &iResponse)) {
        if (iResponse >= 1 && iResponse <= 10 ) {
            if (iResponse == iRandom)
                printf("\nYou guessed right.\n");
            else 
                printf("\nSorry, The correct guess was %d\n", iRandom);
        }
        else
            printf("You did not enter a number between 1 and 10.");
    }
    else
        printf("\nYou did not enter a number.\n");
    return 0;
}

输入

样本输出

Sorry, The correct guess was 9

查看演示 http://ideone.com/V7GIeK。

【讨论】：

【解决方案6】：

尝试制作

char iResponse;

看到这个成功了

【讨论】：