#include<stdio.h>
#include<stdlib.h>
#define MAXCHAR 40

struct node{
	char data;
	struct node * next;
};

int ishs(struct node * head, int n)
{
	char stack[MAXCHAR / 2];
	struct node * p = head; 
	int top = 0;
	while (top < n / 2)//將前半部分元素入棧
	{
		stack[top] = p->data;
		top++;
		p = p->next;
	}
	if (n % 2 == 1)
	{
		p = p->next;
	}
	top--;
	for (int i = 0; i < n / 2; i++)
	{
		printf("%c,", stack[i]);
	}
	while (top >= 0 && p != NULL&&stack[top] == p->data)
	{
		top--;
		p = p->next;
	}
	if (top == -1&&p == NULL)//比較完畢，是迴文
		return 1;
	else
		return 0;
}
int main()
{
	char s[MAXCHAR];
	struct node * head = NULL, *q, *p;
	int i = 0;
	printf("輸入一個數：");
	scanf("%s", s);
	while (s[i] != '\0')
	{
		p = (struct node *)malloc(sizeof(struct node));
		p->data = s[i];
		p->next = NULL;
		if (head == NULL)
		{
			head = p;
			q = p;
		}
		else
		{
			q->next = p;
			q = p;
		}
		i++;
	}
	if (ishs(head, i)==1)
		printf("%s是迴文\n", s);
	else
		printf("%s不是迴文\n", s);
	system("pause");
	return 0;
}