LeetCode 19 Remove Nth Node From End of list

题目

Given a linked list, remove the nth node from the end of list and return its head.

For example,

Given linked list: 1->2->3->4->5, and n = 2.

After removing the second node from the end, the linked list becomes 1->2->3->5.
Note:
Given n will always be valid.
Try to do this in one pass.

思路

为这个list定义一个头指针delNode,而后再定义一个指针指向head,让这俩指针始终保持n的距离,那delNode.next就是须要删除的节点,而后删掉就能够了,注意特别考虑要删除的节点是head的状况,要把head从新指定一下它的位置.

代码

var removeNthFromEnd = function(head, n) {
    if (head == null) {
        return [];
    }
    var delNode = new ListNode(0);
    delNode.next = head;
    var lastNode = head;
    var dis = 1;
    while (lastNode.next !== null) {
        if (dis < n) {
            lastNode = lastNode.next;
            dis++;
        }
        else {
            delNode = delNode.next;
            lastNode = lastNode.next;
        }      
    }

    var temp = delNode.next;
    delNode.next = temp.next;
    if (temp == head)
        head = delNode.next;
    temp.next = null;
    return head;
    
};