g0001_0100.s0002_add_two_numbers.Solution.kt Maven / Gradle / Ivy

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package g0001_0100.s0002_add_two_numbers

// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Math #Linked_List #Recursion
// #Data_Structure_II_Day_10_Linked_List #Programming_Skills_II_Day_15
// #2022_03_22_Time_212_ms_(93.71%)_Space_43.1_MB_(81.36%)

import com_github_leetcode.ListNode

/*
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    fun addTwoNumbers(l1: ListNode?, l2: ListNode?): ListNode? {
        val dummyHead = ListNode(0)
        var p = l1
        var q = l2
        var curr: ListNode? = dummyHead
        var carry = 0
        while (p != null || q != null) {
            val x = p?.`val` ?: 0
            val y = q?.`val` ?: 0
            val sum = carry + x + y
            carry = sum / 10
            curr!!.next = ListNode(sum % 10)
            curr = curr.next
            if (p != null) {
                p = p.next
            }
            if (q != null) {
                q = q.next
            }
        }
        if (carry > 0) {
            curr!!.next = ListNode(carry)
        }
        return dummyHead.next
    }
}