用链表模拟栈机制倒序输出字符串

[mcmay]

各位达人，下面这个程序用链表模拟栈机制倒序输出字符串，但不知问题在哪，麻烦指教！

// exercise 5, chapter 17

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

typedef char Item;

typedef struct node
{
	Item item;
	struct node * next;
	struct node * prev;
}Node;

typedef struct {
	Node * head;
	Node * tail;
}Stack;

int main(void)
{
	char ch;
	Stack stack;
	Node * tmp;

	stack.head = stack.tail = NULL;
	puts("Enter a string:");
	while((ch = getchar())!= '\n' && (ch = getchar()) != EOF)
	{
		tmp = (Node *) malloc(sizeof(Node));
		tmp->item = ch;
		if(tmp == NULL)
		{
			fputs("Failed to allocate memory.", stderr);
			exit(1);
		}
		if(stack.head == NULL)
		{
			stack.head = tmp;
			stack.head->prev = NULL;  //让第一个元素的前溯指针为NULL
		}
		else
		{
			stack.tail->next = tmp;
		        tmp->prev = stack.tail; //让从第二个元素开始的前溯指针指向前一个元素			
		}
		tmp->next = NULL;
		stack.tail = tmp;
	}
	if(stack.head == NULL)
		puts("No string entered.");
	else
	{
		puts("String in reverse:");
		tmp = stack.tail;
		while(tmp != NULL)
		{
			putchar(tmp->item);
			tmp = tmp->prev;
		}
	}

	puts("\nDone!");
	return 0;
}

[707wk]

直接倒序创建链表不就行了吗，要弄这么复杂吗？ 倒序创建链表（仅供参考）

typedef struct node
{
	int num;
	struct node *next;
}NODE;
struct node *crfun(int n)
{
	NODE* head=NULL;
	NODE* p;
	while(n)
	{
		p=(NODE*)malloc(sizeof(NODE));
		scanf("%d",&p->num);
		p->next=head;
		head=p;
		n--;
	}
	return p;
}

[mcmay]

// exercise 5, chapter 17
 
#include <stdio.h>
#include <stdlib.h>
 
typedef char Item;
 
typedef struct node
{
    Item item;
    struct node * next;
    struct node * prev;
}Node;
 
typedef struct {
    Node * head;
    Node * tail;
}Stack;
 
int main(void)
{
    char ch;
    Stack stack;
    Node * tmp;
 
    stack.head = stack.tail = NULL;
    puts("Enter a string:");
    while((ch = getchar())!= '\n' && (ch = getchar()) != EOF)   //我找到了，是这里出了问题
    {                                                                           //(ch = getchar()) != EOF是多读了字符了
        tmp = (Node *) malloc(sizeof(Node));
        tmp->item = ch;
        if(tmp == NULL)
        {
            fputs("Failed to allocate memory.", stderr);
            exit(1);
        }
        if(stack.head == NULL)
        {
            stack.head = tmp;
            stack.head->prev = NULL;  //让第一个元素的前溯指针为NULL
        }
        else
        {
            stack.tail->next = tmp;
                tmp->prev = stack.tail; //让从第二个元素开始的前溯指针指向前一个元素           
        }
        tmp->next = NULL;
        stack.tail = tmp;
    }
    if(stack.head == NULL)
        puts("No string entered.");
    else
    {
        puts("String in reverse:");
        tmp = stack.tail;
        while(tmp != NULL)
        {
            putchar(tmp->item);
            tmp = tmp->prev;
        }
    }
 
    puts("\nDone!");
    return 0;
}