在C中按0时退出[重复]

Question

int main()
{
int program = 0;
while (program >= 0)
{
    printf("\nChoose one of the following programs: \n\n (1) Fibonacci Sequence Calculator \n (2) Decimal and Binary Calculator \n (3) Prime Number Calculator \n \nIf you want to exit the program, press (e).\nYour choice: ");

    scanf("%d", &program);

    if (program == 0)
    {
        printf("Quitting the program...\n\n");
        return 0;
    }

    else if(program==1)
    {
        printf ("FIBONACCI SEQUENCE CALCULATOR");
    }
    else if(program==2)
    {
        printf("DECIMAL AND BINARY CALCULATOR");
    }

    else if(program==3)
    {
        printf("PRIME NUMBER CALCULATOR");
    }

    else
    {
        printf("ERROR");
    }
}

当用户输入除 0、1、2 和 3 以外的任何内容时，我想打印“ERROR”，但这是我输入时的结果：

• 除 0、1、2 和 3 以外的任何数字：“ERROR”（这是正确的）
• 任何字母/符号：“退出程序...”（这应该是“错误”！）

也许这可以帮助我找出问题的答案：我已经知道 %d 用于扫描整数， %c 用于扫描字符。但是当我想同时扫描它们时，我必须使用什么？

任何帮助将不胜感激:)

Answer 1

示例其中一种方式。

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

void end_proc(void){
    printf("Quitting the program...\n\n");
    exit(0);
}

void input_error_proc(void){
    int ch;
    printf("ERROR\n");
    while((ch = getchar()) != '\n' && ch != EOF);//clear input
}

int main(void){
    int program;

    while(1){
        printf("\n"
            "Choose one of the following programs: \n\n"
            " (1) Fibonacci Sequence Calculator \n"
            " (2) Decimal and Binary Calculator \n"
            " (3) Prime Number Calculator \n"
            " \n"
            "If you want to exit the program, press (e or 0).\n"
            "Your choice: ");

        if(1==scanf("%d", &program)){//input number 
            if (program == 0){
                end_proc();
            } else if(program == 1){
                printf ("FIBONACCI SEQUENCE CALCULATOR");
            } else if(program==2) {
                printf("DECIMAL AND BINARY CALCULATOR");
            } else if(program==3) {
                printf("PRIME NUMBER CALCULATOR");
            } else {
                input_error_proc();
            }
        } else {//input not number
            char ch, check;
            if(2 == scanf(" %c%c", &ch, &check) && ch == 'e' && check == '\n')
                end_proc();
            else
                input_error_proc();
        }
    }
    return 0;
}

Answer 2

我添加了 digit 或 char 测试，并更改了您的程序流程。

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

int main() {
    int program = 0;
    char c;
    for (; ;) {
        printf("\nChoose one of the following programs: \n\n (1) Fibonacci Sequence Calculator \n (2) Decimal and Binary Calculator \n (3) Prime Number Calculator \n \nIf you want to exit the program, press (e).\nYour choice: ");

        scanf(" %c", &c);

        if (isalpha(c)) {
            printf("ERROR");
            continue;
        }

        else if (isdigit(c)) {

            program = atoi(&c);

            if (program == 0) {
                printf("Quitting the program...\n\n");
                return 0;
            }

            else if (program == 1) {
                printf("FIBONACCI SEQUENCE CALCULATOR");

            }
            else if (program == 2) {
                printf("DECIMAL AND BINARY CALCULATOR");
            }

            else if (program == 3) {
                printf("PRIME NUMBER CALCULATOR");
            }

            else {
                printf("ERROR");
            }

        }

    }
}

测试

Debug/gnu

Choose one of the following programs: 

 (1) Fibonacci Sequence Calculator 
 (2) Decimal and Binary Calculator 
 (3) Prime Number Calculator 

If you want to exit the program, press (e).
Your choice: 1
FIBONACCI SEQUENCE CALCULATOR
Choose one of the following programs: 

 (1) Fibonacci Sequence Calculator 
 (2) Decimal and Binary Calculator 
 (3) Prime Number Calculator 

If you want to exit the program, press (e).
Your choice: q
ERROR
Choose one of the following programs: 

 (1) Fibonacci Sequence Calculator 
 (2) Decimal and Binary Calculator 
 (3) Prime Number Calculator 

If you want to exit the program, press (e).
Your choice: