README_EN.md

989. Add to Array-Form of Integer

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Description

The array-form of an integer num is an array representing its digits in left to right order.

• For example, for num = 1321, the array form is [1,3,2,1].

Given num, the array-form of an integer, and an integer k, return the array-form of the integer num + k.

 

Example 1:

Input: num = [1,2,0,0], k = 34
Output: [1,2,3,4]
Explanation: 1200 + 34 = 1234

Example 2:

Input: num = [2,7,4], k = 181
Output: [4,5,5]
Explanation: 274 + 181 = 455

Example 3:

Input: num = [2,1,5], k = 806
Output: [1,0,2,1]
Explanation: 215 + 806 = 1021

Example 4:

Input: num = [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

 

Constraints:

• 1 <= num.length <= 104
• 0 <= num[i] <= 9
• num does not contain any leading zeros except for the zero itself.
• 1 <= k <= 104

Solutions

Python3

class Solution:
    def addToArrayForm(self, A: List[int], K: int) -> List[int]:
        n = len(A) - 1
        carry, res = 0, []
        while n >= 0 or K != 0 or carry != 0:
            carry += (0 if n < 0 else A[n]) + (K % 10)
            res.append(carry % 10)
            K //= 10
            carry //= 10
            n -= 1
        return res[::-1]

Java

class Solution {
    public List<Integer> addToArrayForm(int[] A, int K) {
        int n = A.length - 1;
        List<Integer> res = new ArrayList<>();
        int carry = 0;
        while (n >= 0 || K != 0 || carry != 0) {
            carry += (n < 0 ? 0 : A[n]) + (K % 10);
            res.add(carry % 10);
            K /= 10;
            carry /= 10;
            --n;
        }
        Collections.reverse(res);
        return res;
    }
}

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