LeetCode in Kotlin

967. Numbers With Same Consecutive Differences

Medium

Given two integers n and k, return an array of all the integers of length n where the difference between every two consecutive digits is k. You may return the answer in any order.

Note that the integers should not have leading zeros. Integers as 02 and 043 are not allowed.

Example 1:

Input: n = 3, k = 7

Output: [181,292,707,818,929]

Explanation: Note that 070 is not a valid number, because it has leading zeroes.

Example 2:

Input: n = 2, k = 1

Output: [10,12,21,23,32,34,43,45,54,56,65,67,76,78,87,89,98]

Constraints:

• 2 <= n <= 9
• 0 <= k <= 9

Solution

import kotlin.math.abs

@Suppress("NAME_SHADOWING")
class Solution {
    fun numsSameConsecDiff(n: Int, k: Int): IntArray {
        var k = k
        k = abs(k)
        val list: MutableList<Int> = ArrayList()
        dfs(list, 100000, 0, n, k)
        val res = IntArray(list.size)
        for (i in res.indices) {
            res[i] = list[i]
        }
        return res
    }

    private fun dfs(list: MutableList<Int>, can: Int, len: Int, n: Int, k: Int) {
        if (len == n) {
            list.add(can)
            return
        }
        if (can == 0) {
            return
        }
        if (len == 0) {
            for (i in 0..9) {
                dfs(list, i, 1, n, k)
            }
        } else {
            val last = can % 10
            val a = last + k
            val b = last - k
            if (b >= 0) {
                dfs(list, can * 10 + b, len + 1, n, k)
            }
            if (k != 0 && a < 10) {
                dfs(list, can * 10 + a, len + 1, n, k)
            }
        }
    }
}

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