javascript 单向链表反转 reverse 部分反转

leetcode:

https://leetcode.com/problems/reverse-linked-list/

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var reverseList = function(head) {
    var prev = null, cur = head, next;
    
    while (cur !== null) {
        next = cur.next;
        head = cur;
        cur.next = prev;
        prev = cur;
        cur = next;
    }
    return head;
};

https://leetcode.com/problems/reverse-linked-list-ii/description/

Reverse a linked list from position m to n. Do it in one-pass.

Note: 1 ≤ m ≤ n ≤ length of list.

Example:

Input: 1->2->3->4->5->NULL, m = 2, n = 4
Output: 1->4->3->2->5->NULL

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} m
 * @param {number} n
 * @return {ListNode}
 */
var reverseBetween = function(head, m, n) {
    if(head === null) return head;
    if(m===n) return head;
	
    var dummy = new ListNode(0), h = dummy;
    dummy.next = head;
	for (var i = 0; i < m-1; i++) {
		h = h.next;
	}
    var cur = h.next, last = cur.next;

	for (i = 0; i < n - m; i++) {
		cur.next = last.next;
        last.next = h.next;
        h.next = last;
        last = cur.next;
	}
    return dummy.next;
};