标签：des style blog io for ar div line
Given a singly linked list L: L0→L1→…→Ln-1→Ln, reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→…
You must do this in-place without altering the nodes‘ values.
For example, Given {1,2,3,4}, reorder it to {1,4,2,3}.
说明：分三步，1。从中间分开，成两部分。2，后半部分链表逆置。3.插入合并。
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
void reorderList(ListNode *head) {
if(head == NULL) return;
ListNode *p1, *p2, *p3, *head2;
p1 = p2 = head;
while(p2->next && p2->next->next) {
p1 = p1->next;
p2 = p2->next->next;
}
head2 = p1->next; p1 = p1->next = NULL;
p2 = head2;
while(p2) {
p3 = p2->next;
p2->next = p1;
p1 = p2;
p2 = p3;
}
head2 = p1; p1 = head;
while(head2 && p1) {
p2 = head2->next;
head2->next = p1->next;
p1->next = head2;
head2 = p2;
p1 = p1->next->next;
}
}
};
标签：des style blog io for ar div line
原文地址：http://www.cnblogs.com/liyangguang1988/p/3902287.html
