24. 两两交换链表中的节点
注意点
1.终止条件 cur.next != null && cur.next.next != null
2.操作cur后两个节点
3.操作完成后，链表更改 cur = temp;
/**
* Definition for singly-linked list.
* function ListNode(val, next) {
* this.val = (val===undefined ? 0 : val)
* this.next = (next===undefined ? null : next)
* }
*/
/**
* @param {ListNode} head
* @return {ListNode}
*/
var swapPairs = function(head) {
let dummyHead = new ListNode(0,head);
let cur = dummyHead;
while (cur.next != null && cur.next.next != null) {
let temp = cur.next;
let temp1 = temp.next.next;
cur.next = temp.next;
temp.next.next = temp;
temp.next = temp1;
cur = temp;
}
return dummyHead.next;
};
19. 删除链表的倒数第 N 个结点
/**
* Definition for singly-linked list.
* function ListNode(val, next) {
* this.val = (val===undefined ? 0 : val)
* this.next = (next===undefined ? null : next)
* }
*/
/**
* @param {ListNode} head
* @param {number} n
* @return {ListNode}
*/
var removeNthFromEnd = function(head, n) {
let dummyHead = new ListNode(0,head);
let slow = dummyHead, fast = dummyHead;
// fast先移动n步
while (n && fast != null) {
fast = fast.next;
n--;
}
fast = fast.next;
while (fast != null) {
fast = fast.next;
slow = slow.next;
}
slow.next = slow.next.next;
return dummyHead.next;
};
