LeetCode [989] Add to Array-Form of Integer

 989. Add to Array-Form of Integer

Easy

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

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class Solution { public List<Integer> addToArrayForm(int[] A, int K) { List<Integer> B = new ArrayList<>(); while(K>0){ B.add(K%10); K = K/10; } List<Integer> ret = new ArrayList<>(); int c = 0, nb = B.size(), j = 0; for(int i=A.length-1; i>=0; --i, ++j){ int r = A[i]+c; if(j<nb) r += B.get(j); ret.add(r%10); c = r/10; } while(j<nb){ int r = B.get(j++) + c; ret.add(r%10); c = r/10; } if(c>0) ret.add(c); Collections.reverse(ret); return ret; } }