swapPairs

Given a linked list, swap every two adjacent nodes and return its head.

For example,
Given 1->2->3->4, you should return the list as 2->1->4->3.

Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.

---

public class Solution {
public ListNode swapPairs(ListNode head) {
ListNode start = new ListNode(0);
start.next = head;
for(ListNode cur = start; cur.next != null && cur.next.next != null; cur = cur.next.next) {
cur.next = swap(cur.next, cur.next.next);
}
return start.next;
}
private Listnode swap(ListNode next1, ListNode next2) {
next1.next = next2.next;
next2.next = next1;
return next2;
}
}
运用了递归的思想，解决问题前化大为小，思考时候是否能够重复某一个小的步骤来解决一个问题。@mike3 from leetcode discusstion

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