g0201_0300.s0206_reverse_linked_list.Solution.scala Maven / Gradle / Ivy

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104 LeetCode algorithm problem solutions

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package g0201_0300.s0206_reverse_linked_list

// #Easy #Top_100_Liked_Questions #Top_Interview_Questions #Linked_List #Recursion
// #Data_Structure_I_Day_8_Linked_List #Algorithm_I_Day_10_Recursion_Backtracking
// #Level_1_Day_3_Linked_List #Udemy_Linked_List #Big_O_Time_O(N)_Space_O(1)
// #2023_11_05_Time_474_ms_(87.50%)_Space_57.4_MB_(18.06%)

import com_github_leetcode.ListNode

/*
 * Definition for singly-linked list.
 * class ListNode(_x: Int = 0, _next: ListNode = null) {
 *   var next: ListNode = _next
 *   var x: Int = _x
 * }
 */
object Solution {
    def reverseList(head: ListNode): ListNode = {
        var prev: ListNode = null
        var curr = head

        while (curr != null) {
            val next = curr.next
            curr.next = prev
            prev = curr
            curr = next
        }
        prev
    }
}