尝试在 C 中实现带有两个堆栈的队列时出现意外行为

我正在处理一个非常常见的问题，即用两个堆栈实现队列并用 C 语言完成，因为这给了我一个借口来复习结构和指针的知识。

我分别借助 struct 创建了两个堆栈变量 st1 和 st2 。我将元素推送到 st1 进行入队操作，对于出队，从 st1 弹出元素并同时推送到 st2 。弹出 st2 后，元素再次转移回 st1 （我知道这是多余的，但这不是我面临的问题）。所有这些都已在 中的 switch case 中使用相应的函数实现main()。

该错误是，当调用出队操作时，st1 的第一个元素会被其他值神秘地覆盖。

完整代码如下：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
typedef struct stack
{
    char name[5] ;
    int top ; 
    int *a ; 
}Stack ;
int n ; 
int main()
{
    void push(Stack*,int) ; 
    int delete(Stack*,Stack*) ;
    void display(Stack*) ;
    printf("Enter the size of the queue: ") ;
    scanf("%d",&n) ;
    Stack st1,st2 ; 
    st1.a = (int*)malloc(n*sizeof(int)) ;
    st1.top = -1 ; 
    st2 = st1 ;
    strcpy(st1.name,"st1") ;
    strcpy(st2.name,"st2") ;
    while(1)
    {
        printf("Enter 1. to insert.\nEnter 2. to delete.\nEnter 3. to display.\nEnter anything else to exit.\n") ; 
        char c ; 
        int e ;
        scanf(" %c",&c) ; 
        switch(c)
        {
            case '1': 
            printf("Enter the no. to be inserted: ") ;
            scanf("%d",&e) ; 
            push(&st1,e) ;
            break ; 
            case '2' :
            e = delete(&st1,&st2) ; 
            printf("%d got deleted.\n",e) ;
            break ; 
            case '3' : 
            display(&st1) ;
            break ; 
            default : 
            free(st1.a) ; 
            free(st2.a) ; 
            return 0 ;
        }
    }
}
int delete(Stack *st1,Stack *st2)
{
    void push(Stack*,int) ; 
    int pop(Stack*) ;
    while(st1->top!=-1)
    push(st2,pop(st1)) ;

    int e = pop(st2) ; 

    while(st2->top!=-1)
    push(st1,pop(st2)) ;

    return e ;
}
void push(Stack *st,int e)
{
    void display(Stack*) ;
    printf("Operations on %s begin: \n",st->name) ;
    printf("Currently %s:\n",st->name) ;
    display(st) ;
    st->top++ ; 
    if(st->top==n)
    {
        printf("Queue full.\n") ;
        st->top-- ;
        return ; 
    }
    st->a[st->top] = e ;
    printf("After operations , %s:\n",st->name) ;
    display(st) ;
    printf("Operations on %s end.\n\n",st->name) ;
}
int pop(Stack *st)
{
    void display(Stack*) ;
    printf("Operations on %s begin: \n",st->name) ;
    display(st) ;
    if(st->top==-1)
    {
        printf("Queue is empty.\n") ;
        return -1 ;
    }
    int e = st->a[st->top] ; 
    st->top-- ; 
    printf("After operations , %s:\n",st->name) ;
    display(st) ;
    printf("Operations on %s end.\n\n",st->name) ;
    return e ;
}
void display(Stack *st)
{
    if(st->top==-1)
    {
        printf("Queue is empty.\n") ;
        return ;
    }
    int i ;
    for(i=0;i<=st->top;i++)
    printf("%d ",st->a[i]) ;
    printf("\n") ;
}

如您所见，我已经编写了printf()用于调试的语句。以下是输出，您可以看到错误：

Enter the size of the queue: 5
Enter 1. to insert.
Enter 2. to delete.
Enter 3. to display.
Enter anything else to exit.
1
Enter the no. to be inserted: 1
Operations on st1 begin: 
Currently st1:
Queue is empty.
After operations , st1:
1 
Operations on st1 end.

Enter 1. to insert.
Enter 2. to delete.
Enter 3. to display.
Enter anything else to exit.
1
Enter the no. to be inserted: 2
Operations on st1 begin: 
Currently st1:
1 
After operations , st1:
1 2 
Operations on st1 end.

Enter 1. to insert.
Enter 2. to delete.
Enter 3. to display.
Enter anything else to exit.
2
Operations on st1 begin: 
1 2 
After operations , st1:
1 
Operations on st1 end.

Operations on st2 begin: 
Currently st2:
Queue is empty.
After operations , st2:
2 
Operations on st2 end.

Operations on st1 begin: 
2 
After operations , st1:
Queue is empty.
Operations on st1 end.

Operations on st2 begin: 
Currently st2:
2 
After operations , st2:
2 2 
Operations on st2 end.

Operations on st2 begin: 
2 2 
After operations , st2:
2 
Operations on st2 end.

Operations on st2 begin: 
2 
After operations , st2:
Queue is empty.
Operations on st2 end.

Operations on st1 begin: 
Currently st1:
Queue is empty.
After operations , st1:
2 
Operations on st1 end.

2 got deleted.
Enter 1. to insert.
Enter 2. to delete.
Enter 3. to display.
Enter anything else to exit.

您可以看到，当我调用出队操作时，从 st1 弹出 2 并将其推入 st2 之后，0st1 的第 th 索引从 更改1为2。

这个问题困扰了我好久。我以为是指针出了问题，所以我把所有指针都删除了，然后做了同样的事情，但通过值传递了堆栈变量。当我这样做时，出现了一个更大的问题，每次我插入一个值时，它都会以某种方式自动被删除。所以当我下次尝试插入时，之前的插入已经消失了。

我觉得存在一些导致这些问题的根本问题，需要解决这些问题才能使代码正常运行。