leetcode/src/234.c at master · lennylxx/leetcode · GitHub

Name: leetcode/src/234.c at master · lennylxx/leetcode · GitHub
Rating: 4.9 (8585 reviews)
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#include<stdio.h>
#include<stdlib.h>
#include<stdbool.h>

structListNode {
intval;
structListNode*next;
};

boolisPalindrome(structListNode*head) {
if (head==NULL) return true;

structListNode*p=head;
intlen=0;
while (p) {
len++;
p=p->next;
 }

inthalf=len / 2;

/* get the middle node */
p=head;
while (half--) {
p=p->next;
 }

/* skip middle if length is odd */
if (len % 2==1) {
p=p->next;
 }

/* reverse the right half */
structListNode*prev=NULL, *next=NULL;
while (p) {
next=p->next;
p->next=prev;
prev=p;
p=next;
 }

structListNode*q=prev;
p=head;
half=len / 2;

while (half--) {
if (p->val!=q->val)
return false;
p=p->next;
q=q->next;
 }

return true;
}

voidprintList(structListNode*head) {
if (head==NULL) return;

while (head) {
printf("%d->", head->val);
head=head->next;
 }
printf("N\n");
}

intmain() {

structListNode*l1= (structListNode*)calloc(4, sizeof(structListNode));
structListNode*l2= (structListNode*)calloc(5, sizeof(structListNode));

structListNode*p=l1;

p->val=1;
p->next=l1+1;
p=p->next;

p->val=2;
p->next=l1+2;
p=p->next;

p->val=2;
p->next=l1+3;
p=p->next;

p->val=1;
p->next=NULL;

p=l2;
p->val=1;
p->next=l2+1;
p=p->next;

p->val=2;
p->next=l2+2;
p=p->next;

p->val=3;
p->next=l2+3;
p=p->next;

p->val=2;
p->next=l2+4;
p=p->next;

p->val=1;
p->next=NULL;

printList(l1);
printf("%d\n", isPalindrome(l1));

printList(l2);
printf("%d\n", isPalindrome(l2));

return0;
}