Problem
You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
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/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { * val = x; * next = null; * } * } */ public ListNode addTwoNumbers_3(ListNode l1, ListNode l2) { } |
Solution
Time complexity: o(n).
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/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { * val = x; * next = null; * } * } */ public ListNode addTwoNumbers_3(ListNode l1, ListNode l2) { List<Integer> lst = new ArrayList<Integer>(); int overflow = 0; while(l1 != null || l2 != null) { int sum = 0; if(l1 != null) { sum += l1.val; l1 = l1.next; } if(l2 != null) { sum += l2.val; l2 = l2.next; } sum += overflow; if(sum > 9) { sum = sum - 10; overflow = 1; } else { overflow = 0; } lst.add(0, sum); } if(overflow == 1) { // don't forget the last overflow / carry bit check lst.add(0, 1); } ListNode node = null; ListNode tmp = null; for(Integer val : lst) { tmp = node; node = new ListNode(val); node.next = tmp; } return node; } |
