addToArrayForm.go

/* 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 <= A.length <= 10000
	0 <= A[i] <= 9
	0 <= K <= 10000
	If A.length > 1, then A[0] != 0
*/
package larray

func addToArrayForm(A []int, K int) []int {
	if K == 0 {
		return A
	}

	res, carry := make([]int, 0, len(A)), 0
	for i := len(A) - 1; K != 0 || i >= 0; i-- {
		sum := K%10 + carry
		if i >= 0 {
			sum += A[i]
		}
		carry = sum / 10
		res = append(res, sum%10)
		K /= 10
	}
	if carry == 1 {
		res = append(res, 1)
	}

	for i := 0; i < len(res)/2; i++ {
		res[i], res[len(res)-1-i] = res[len(res)-1-i], res[i]
	}
	return res
}