数据结构与算法每日一题——链表(92. 反转链表 II)

92. 反转链表 II

#### 一次遍历「穿针引线」反转链表（头插法）
/**
 * 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} left
 * @param {number} right
 * @return {ListNode}
 */
var reverseBetween = function (head, left, right) {
    let dummyHead = new ListNode(0, head)
    let pre = dummyHead
    dummyHead.next = head
    for(let i=0;i<left-1;i++){
        pre = pre.next
    }
    let cur = pre.next
    for(let i=0;i<right-left;i++){
        let next =cur.next
        cur.next =next.next
        next.next =pre.next
        pre.next = next
    }
    return dummyHead.next
};