解题思路

相关代码

/*** Definition for singly-linked list.* public class ListNode {*     int val;*     ListNode next;*     ListNode() {}*     ListNode(int val) { this.val = val; }*     ListNode(int val, ListNode next) { this.val = val; this.next = next; }* }*/
class Solution {public void reorderList(ListNode head) {Stack<Integer> stack = new Stack<>();ListNode t1 = head;while(t1!=null){stack.push(t1.val);t1=t1.next;}//奇不动，偶动。int length = stack.size();ListNode H = new ListNode(-11);ListNode p1 = head;ListNode p2 = H;for(int i=1;i<=length;i++){if(i%2==1){ListNode temp1 = new ListNode(p1.val);p2.next = temp1;p2=p2.next;}else{ListNode temp2 = new ListNode(stack.pop());p2.next = temp2;p2=p2.next;p1=p1.next;}}ListNode f1 = head;ListNode f2 = H.next;while(f1!=null){f1.val = f2.val;f1=f1.next;f2=f2.next;}}
}