You are given two non-empty linked lists representing two non-negative integers. The digits are stored in order and each of their nodes contains a single digit. Add the two numbers and return them as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.
Example:
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 8 -> 0 -> 7
Explanation: 342 + 465 = 807.Solution:
using System;
using System.Collections.Generic;
using System.Text;
namespace LeetCode.Medium
{
//Definition for singly-linked list.
public class ListNode {
public int val;
public ListNode next;
public ListNode(int x) { val = x; }
}
class AddTwoNumbersSolution
{
public void execute()
{
var l1 = new ListNode(2);
l1.next = new ListNode(4);
l1.next.next = new ListNode(3);
var l2 = new ListNode(5);
l2.next = new ListNode(6);
l2.next.next = new ListNode(4);
AddTwoNumbers(l1, l2);
}
public ListNode AddTwoNumbers(ListNode l1, ListNode l2)
{
var res = new ListNode(0);
int len1 = FindLength(l1);
int len2 = FindLength(l2);
int diff1 = 0;
int diff2 = 0;
if (len1 > len2)
{
diff1 = len1 - len2;
while(diff1 != 0)
{
var temp = new ListNode(0);
temp.next = l2;
l2 = temp;
}
}
else
{
diff2 = len2 - len1;
while (diff2 != 0)
{
var temp = new ListNode(0);
temp.next = l1;
l1 = temp;
}
}
res = Calculate(l1,l2);
return res;
}
private ListNode Calculate(ListNode l1, ListNode l2)
{
int carry=0;
var node = CalculateRecursively(l1, l2, ref carry);
if(carry == 1)
{
var temp = new ListNode(carry);
temp.next = node;
node = temp;
}
return node;
}
private ListNode CalculateRecursively(ListNode l1, ListNode l2, ref int carry)
{
if (l1 == null)
{
carry = 0;
return null;
}
var node = CalculateRecursively(l1.next, l2.next, ref carry);
int sum = l1.val + l2.val +carry;
carry = sum / 10;
var currentNode = new ListNode(sum % 10);
currentNode.next = node;
return currentNode;
}
private int FindLength(ListNode l1)
{
int len = 0;
//ListNode temp = l1;
while(l1 != null)
{
len++;
l1 = l1.next;
}
return len;
}
}
}Time Complexity: O(n) - as it is going through all nodes.
Space Complexity: O(n) - as the recursive call is creating a stack.
