为什么goto循环不能继续下去？

Question

按照我的设想，应该重回loop位置后再有scanf请求输入的，然后到switch继续循环，但是运行结果确实直接跳过去了，为什么？

#include<stdio.h>
#include<string.h>

typedef struct {
    int sit_num;
    int order;
    char nachname[20];
    char vorname[20];
}plane;
 
void plan_a(plane *p);
void plan_b(plane *p);
void plan_c(plane *p);
void plan_d(plane *p);
void plan_e(plane *p);



int main() {
    plane A[11]={};//运行前自行初始化录入数据 
    



    loop: printf("To choose a functions, enter its letter label:\n");
    printf("a)    Show number of empty seats\n");
    printf("b)    Show list of empty seats\n");
    printf("c)    Show alphabetical list of seats\n");
    printf("d)    Assign a customer to a seat assignment\n");
    printf("e)    Delete a seat assignment\n");
    printf("f)    Quit\n");
    char n, m;
    scanf("%c", &n);
    if (n == 'f')
        goto q2;
    switch (n)
    {
    case 'a':plan_a(A); goto loop; break;
    case 'b':plan_b(A); goto loop; break;
    case 'c':plan_c(A); goto loop; break;
    case 'd':plan_d(A); goto loop; break;
    case 'e':plan_e(A); goto loop; break;
    case 'f':break;

    default:
        break;
    }


q2:printf("程序结束");
    return 0;
}


void plan_a(plane *p) {
    int LL = 0;
    
    printf("如要中止，请按1后回车；如需继续，请按0后回车");
    scanf("%d", &LL);
    if (LL == 1)
        goto qq;


    int sum_order = 0;
    int i=0;
    for (i = 0; i < 12; i++) {
        if ((p+i)->order == 0)
            sum_order = sum_order + 1;
    }
    printf("%d\n", sum_order);


qq:if (LL == 1)
    printf("返回菜单");
}
void plan_b(plane *p) {
    int LL = 0;

    printf("如要中止，请按1后回车；如需继续，请按0后回车");
    scanf("%d", &LL);
    int i=0;
    if (LL == 1){
    
        goto qq;}


    for (i = 0; i < 12; i++)
    {
        if ((p+i)->order == 0)
            printf("%d\n", (p+i)->sit_num);
    }


qq:if (LL == 1)
    printf("返回菜单");
}
void plan_c(plane *p) {
    int LL = 0;
    printf("如要中止，请按1后回车；如需继续，请按0后回车");
    scanf("%d", &LL);
    if (LL == 1)
        goto qq;

    int i=0;
    for (i = 0; i < 12; i++)
    {
        printf("%d\n", (p + i)->sit_num);
    }

qq:if (LL == 1)
    printf("返回菜单");
}
void plan_d(plane *p) {
    int LL = 0;
    printf("如要中止，请按1后回车；如需继续，请按0后回车");
    scanf("%d", &LL);
    if (LL == 1)
        goto qq;

    int L2 = 0;
        printf("请输入预订座位号\n");
        scanf("%d", &L2);
        (p + L2)->order = 1;
        printf("请输入预订人的名\n");
        scanf("%s", &(p + L2)->nachname);
        printf("请输入预定人的姓\n");
        scanf("%s", &(p + L2)->vorname);

    qq:if (LL == 1)
        printf("返回菜单");
}
void plan_e(plane *p) {
    int LL = 0;
    printf("如要中止，请按1后回车；如需继续，请按0后回车");
    scanf("%d", &LL);
    if (LL == 1)
        goto qq;


    int L3 = 0;
    printf("请输入删除座位编号");
    scanf("%d", &L3);
    char zero[20] = { 0 };
    strcpy((p + L3)->nachname, zero);
    strcpy((p + L3)->vorname, zero);
    (p + L3)->order = 0;
qq:if (LL == 1)
    printf("返回菜单");

}

Answer 1

主要是你每个plane_a到plane_e函数中都有scanf输入。输入数据后你按了回车键，导致goto loop后，scanf("%c",&n)会自动接收这个换行符，从而switch的时候执行了default，break掉了
你在plane_a到plane_e的scanf语句后，调用getchar();消化掉换行符就好了