Leetcode: Add to Array-Form of Integer

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Add to Array-Form of Integer

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Similar Problems:

• LeetCode: Add Strings
• CheatSheet: Leetcode For Code Interview
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• Tag: #array

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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

• 0 <= A[i] <= 9
• 0 <= K <= 10000
• If A.length > 1, then A[0] != 0

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

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// https://code.dennyzhang.com/add-to-array-form-of-integer
// Basic Ideas: add big numbers
// Complexity: Time O(n), Space O(1)
import "strconv"
func addToArrayForm(A []int, K int) []int {
    length := len(strconv.Itoa(K))
    if length < len(A) { length = len(A) }
    length++

    res := make([]int, length)
    num1, num2, carry := 0, 0, 0
    i := len(A)-1
    
    for j:= length-1; j>=0; j-- {
        if i<0 {
            num1 = 0
        } else {
            num1 = A[i]
            i--
        }
        num2, K = K%10, K/10
        res[j] = (num1+num2+carry)%10
        carry = (num1+num2+carry)/10
    }
    j:=0
    for ; j<len(res)-1 && res[j]==0; j++ {
    }
    return res[j:]
}