CVisualStudiogoto跳過scanf_s

我在 Visual Studio 上用 C 語言撰寫代碼，但似乎無法解決 scanf_s 掃描一次的問題。

#include <stdio.h>
#include <string.h>
int main() {
    int duration;
    int cost;
    printf("1 day = 50$\nFor students:\n2 days = 90$\n3 days = 120$\n");
    question_1:
    printf("What's your stay duration in days?\n");
    scanf_s("%d", &duration);
    if (duration == 1)
    {
        printf("That will be 50$.");
    }
    else
    {
        if (duration == 2 || duration == 3)
        {
        question_2:
            printf("Are you a student?\n");
            char answer[20];
            scanf_s("%s", &answer, sizeof(answer));
            if (strcmp(answer, "yes") == 0)
            {
                    if (duration == 2)
                    {
                        printf("That will be 90$.");
                    }
                    else
                    {
                        printf("That will be 120$.");
                    }
            }
            else
            {
                if (strcmp(answer, "no") == 0)
                {
                    cost = duration * 50;
                    printf("That will be %d$.", cost);
                }
                else
                {
                    goto question_2;
                }
            }
        }
        else
        {
            goto question_1;
        }
    }
}

當輸入一個單詞而不是數字來表示“持續時間”時，程式會重復列印“你的停留時間是多少天？” 而不是掃描另一個輸入，我應該改變什么？

uj5u.com熱心網友回復：

您需要在輸入無效后清除輸入緩沖區。例如

printf("1 day = 50$\nFor students:\n2 days = 90$\n3 days = 120$\n");

question_1:;
int result;
do
{
    printf("What's your stay duration in days?\n");
    result = scanf_s("%d", &duration);

    if ( result != 1 )
    {
        while ( getchar() != '\n' );
    }
} while ( result != 1 );

請注意，使用回圈而不是 goto 陳述句和標簽要好得多。嘗試使用回圈重寫您的程式。

還要注意標簽后面的分號

question_1:;

問題是在 C 中你不能在宣告之前放置標簽。所以空陳述句有助于解決問題。

uj5u.com熱心網友回復：

此版本的代碼按我、發帖人和 C 新手的意圖作業。

#include <stdio.h>
#include <string.h>
int main() {
    int duration;
    int cost;
    int check;
    printf("1 day = 50$\nFor students:\n2 days = 90$\n3 days = 120$\n");
    question_1:
    do
    {
        printf("What's your stay duration in days?\n");
        check = scanf_s("%d", &duration);

        if (check != 1)
        {
            while (getchar() != '\n');
        }
    } while (check != 1);
    if (duration == 1)
    {
        printf("That will be 50$.");
    }
    else
    {
        if (duration == 2 || duration == 3)
        {
        question_2:
            printf("Are you a student?\n");
            char answer[20];
            scanf_s("%s", &answer, sizeof(answer));
            if (strcmp(answer, "yes") == 0)
            {
                    if (duration == 2)
                    {
                        printf("That will be 90$.");
                    }
                    else
                    {
                        printf("That will be 120$.");
                    }
            }
            else
            {
                if (strcmp(answer, "no") == 0)
                {
                    cost = duration * 50;
                    printf("That will be %d$.", cost);
                }
                else
                {
                    goto question_2;
                }
            }
        }
        else
        {
            goto question_1;
        }
    }
}

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