#967 - Numbers With Same Consecutive Differences

Medium • View on LeetCode • View on GitHub

Problem Description

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.

Solution

/**
 * @param {number} n
 * @param {number} k
 * @return {number[]}
 */
var numsSameConsecDiff = function(n, k) {
  const result = [];

  for (let digit = 1; digit <= 9; digit++) {
    buildNumber(digit, n - 1);
  }

  return result;

  function buildNumber(current, digitsLeft) {
    if (digitsLeft === 0) {
      result.push(current);
      return;
    }

    const lastDigit = current % 10;

    if (lastDigit + k <= 9) {
      buildNumber(current * 10 + lastDigit + k, digitsLeft - 1);
    }

    if (k !== 0 && lastDigit - k >= 0) {
      buildNumber(current * 10 + lastDigit - k, digitsLeft - 1);
    }
  }
};