Add to Array-Form of Integer, Lists Manipulation

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Problem: https://leetcode.com/problems/add-to-array-form-of-integer/description/

For a non-negative integer X, the array-form of X is an array of its digits in left to right order.  For example, if X = 1231, then the array form is [1,2,3,1].
Given the array-form A of a non-negative integer X, return the array-form of the integer X+K.

    Example 1:
    Input: A = [1,2,0,0], K = 34
Output: [1,2,3,4]
Explanation: 1200 + 34 = 1234
    Example 2:
    Input: A = [2,7,4], K = 181
Output: [4,5,5]
Explanation: 274 + 181 = 455
    Example 3:
    Input: A = [2,1,5], K = 806
Output: [1,0,2,1]
Explanation: 215 + 806 = 1021
    Example 4:
    Input: A = [9,9,9,9,9,9,9,9,9,9], K = 1
Output: [1,0,0,0,0,0,0,0,0,0,0]
Explanation: 9999999999 + 1 = 10000000000

    Note：
    1. 1 <= A.length <= 10000
    2. 0 <= A[i] <= 9
    3. 0 <= K <= 10000
    4. If A.length > 1, then A[0] != 0
    Key is to use list manipulations in your preferred language, in my case, C#. Below, thx, ACC.


    public class Solution
{
 public IList AddToArrayForm(int[] A, int K)
 {
  LinkedList retVal = new LinkedList();
  foreach (int a in A) retVal.AddFirst(a);

  LinkedListNode node = retVal.First;
  int carryOver = 0;
  while (node != null && K > 0)
  {
   int temp = node.Value;
   node.Value = (temp + K % 10 + carryOver) % 10;
   carryOver = (temp + K % 10 + carryOver) / 10;
   node = node.Next;
   K /= 10;
  }
  while (node != null)
  {
   int temp = node.Value;
   node.Value = (temp + carryOver) % 10;
   carryOver = (temp + carryOver) / 10;
   node = node.Next;
  }
  while (K > 0)
  {
   retVal.AddLast((K % 10 + carryOver) % 10);
   carryOver = (K % 10 + carryOver) / 10;
   K /= 10;
  }
  if (carryOver > 0)
  {
   retVal.AddLast(carryOver);
  }

  List list = new List();
  for (LinkedListNode n = retVal.Last; n != null; n = n.Previous)
  {
   list.Add(n.Value);
  }

  return list;
 }
}

    Comments

    1. TarasFebruary 14, 2019 at 11:31 PM

      I have decided to merge all checks into a single loop:

      class Solution:
      def addToArrayForm(self, A: 'List[int]', K: int) -> 'List[int]':
      carry, idx, result = 0, len(A) - 1, []
      while K > 0 or idx >= 0 or carry:
      old_digit, idx = A[idx] if idx >= 0 else 0, idx - 1
      sum, K = old_digit + (K % 10) + carry, K // 10
      carry = sum // 10
      result.append(sum % 10)

      return list(reversed(result))

      https://gist.github.com/ttsugriy/dad95e836845bdb22ee44358b115f2e4

      In general pointer based data structures like linked list are extremely inefficient even for everything but making lots of removals/additions in the middle of the collection because they are very cache-unfriendly. Double linked list is also using a lot of memory which explains why the memory footprint is 25.8MB (for comparison the Python implementation above is using 12.7MB). If I weren't so lazy I would preallocate an array of the size of A + 1 and use it instead of using dynamically sized DS like vector/ArrayList :)

      ReplyDelete

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