leetcode 25. K 个一组翻转链表

/**
 * 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} k
 * @return {ListNode}
 */
var reverseKGroup = function(head, k) {
    let cnt = 0;
    let curp = head;
    while(curp){
        cnt++;
        curp = curp.next;
        if(cnt>=k){
            break;
        }
    }
    if(cnt<k){
        return head;
    }else{
        let newson = head;
        let newfa = head.next;
        let oldfa = null;
        let cnt = k;
        while(--cnt){
            let tem = newfa.next;
            newfa.next = newson;
            newson.next = oldfa;
            oldfa = newson;
            newson = newfa;
            newfa = tem;
        }
        head.next = reverseKGroup(newfa,k);
        return newson;
    }
}

该题本质上是翻转链表的变体。

解法需要结合 递归+翻转链表。代码思路还是非常清晰的。