题解 | #牛群旋转#

class ListNode {
    val: number
    next: ListNode | null
    constructor(val?: number, next?: ListNode | null) {
        this.val = (val === undefined ? 0 : val)
        this.next = (next === undefined ? null : next)
    }
}

/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param head ListNode类 
 * @param k int整型 
 * @return ListNode类
 */
export function rotateLeft(head: ListNode, k: number): ListNode {
    // write code here
    let leftNode: ListNode = head
    let rightNode: ListNode = head

    let index: number = 0

    let length = 0
    let countNode = head
    while (countNode) {
        countNode = countNode.next
        length++
    }

    let K = k % length
    if (K === 0) {
        return head
    }

    while (index < K + 1) {
        rightNode = rightNode.next
        index++
    }

    while (rightNode !== null) {
        leftNode = leftNode.next
        rightNode = rightNode.next
    }

    let dummy = new ListNode(-1)
    let curr = dummy
    dummy.next = leftNode.next
    leftNode.next = null

    while (curr.next) {
        curr = curr.next
    }
    curr.next = head

    return dummy.next
}