LeetCode-in-All

148. Sort List

Medium

Given the head of a linked list, return the list after sorting it in ascending order.

Example 1:

Input: head = [4,2,1,3]

Output: [1,2,3,4]

Example 2:

Input: head = [-1,5,3,4,0]

Output: [-1,0,3,4,5]

Example 3:

Input: head = []

Output: []

Constraints:

• The number of nodes in the list is in the range [0, 5 * 104].
• -105 <= Node.val <= 105

Follow up: Can you sort the linked list in O(n logn) time and O(1) memory (i.e. constant space)?

Solution

import { ListNode } from '../../com_github_leetcode/listnode'

/*
 * Definition for singly-linked list.
 * 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)
 *     }
 * }
 */

function sortList(head: ListNode | null): ListNode | null {
    if (!head) return null
    let array = []
    while (head) {
        array.push([head, head.val])
        head = head.next
    }
    array.sort((a, b) => {
        return a[1] - b[1]
    })
    for (let iter = 0; iter < array.length; iter++) {
        if (iter + 1 >= array.length) array[iter][0].next = null
        else array[iter][0].next = array[iter + 1][0]
    }
    return array[0][0]
}

export { sortList }

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