0989. Add to Array Form of Integer

# 989. Add to Array-Form of Integer#

## 题目 #

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`

## 解题思路 #

• 简单题，计算 2 个非负整数的和。累加过程中不断的进位，最终输出到数组中记得需要逆序，即数字的高位排在数组下标较小的位置。

## 代码 #

``````package leetcode

func addToArrayForm(A []int, K int) []int {
res := []int{}
for i := len(A) - 1; i >= 0; i-- {
sum := A[i] + K%10
K /= 10
if sum >= 10 {
K++
sum -= 10
}
res = append(res, sum)
}
for ; K > 0; K /= 10 {
res = append(res, K%10)
}
reverse(res)
return res
}

func reverse(A []int) {
for i, n := 0, len(A); i < n/2; i++ {
A[i], A[n-1-i] = A[n-1-i], A[i]
}
}
``````

Apr 8, 2023