CheckPalindrom int LinkedList 

 1 public static boolean(ListNode l1,ListNode l2){
 2     boolean res = false;
 3     int [] check = {-1};
 4     ListNode mid = getMid(head,check);
 5     if( check[0]==1){
 6     ListNode next = mid.next;
 7     ListNode newHead =reverse(next);
 8     res=checkPalidrom(head, newHead  );
 9     newHead =reverse(newHead);
10     mid.next = newHead;
11     }
12     else if(check[0]==0){
13     ListNode next = mid.next;
14     ListNode newHead =reverse(next);
15     res = checkPalidrom(head, newHead );
16     newHead =reverse(newHead);
17     mid.next = newHead;
18     }
19     return res;
20 }
21 
22 public static ListNode reverse(ListNode head){
23     if(head==null || head.next==null) return head;
24     ListNode cur = head, post = head.next;
25     while(post!=null){
26         ListNode temp = post.next;
27         post.next = cur;
28         cur = post;
29         post = temp;
30     }
31     head.next = null;
32     return cur;
33 }            
34 
35 public static ListNode getMid (ListNode l1, int[] check){
36         ListNode fast = l1,slow = l1;
37     while(true){
38             fast = fast.next;
39             if(fast==null) {check[0]=1; return slow; };
40             fast = fast.next;
41             if(fast==null) { check[0]=0; return slow;};
42             slow=slow.next;
43             if(slow==fast) return slow;
44         }
45 }
46 public static boolean checkPalidrom(ListNode l1,ListNode l2 ){
47     while(l1!=null && l2!=null){
48     if(l1.val!=l2.val) return false;
49         l1 = l1.next;
50         l2 = l2.next;
51     }
52     return true;
53 }
View Code

1 find the mid of the list

2check the len is odd or even 

3 reverse

4compare

5recover

posted @ 2014-02-26 02:47  krunning  阅读(306)  评论(0)  编辑  收藏  举报