967. Numbers With Same Consecutive Differences

Return all non-negative integers of length n such that the absolute difference between every two consecutive digits is k.

Note that every number in the answer must not have leading zeros except for the number 0 itself. For example, 01 has one leading zero and is invalid, but 0 is valid.

You may return the answer in any order.

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]

Example 3:

Input: n = 2, k = 0
Output: [11,22,33,44,55,66,77,88,99]

Example 4:

Input: n = 2, k = 1
Output: [10,12,21,23,32,34,43,45,54,56,65,67,76,78,87,89,98]

Example 5:

Input: n = 2, k = 2
Output: [13,20,24,31,35,42,46,53,57,64,68,75,79,86,97]

Constraints:

• 2 <= n <= 9
• 0 <= k <= 9

# @lc code=start
using LeetCode

function nums_same_consec_diff(n::Int, k::Int)
    (k == 0) && return [(10 ^ n - 1) ÷ 9 * i for i in 1:9]
    function nums_same_consec_diff(n::Int, k::Int, pre::Int)
        (pre < 0 || pre > 9) && return String[]
        (n == 0) && return [""]
        n1, n2 = pre - k, pre + k
        r1 = nums_same_consec_diff(n - 1, k, n1)
        r2 = nums_same_consec_diff(n - 1, k, n2)
        [[string(n1) * r for r in r1]; [string(n2) * r for r in r2]]
    end
    res = Int[]
    for i in 1:9
        tmp = nums_same_consec_diff(n - 1, k, i)
        append!(res, parse(Int, string(i) * t) for t in tmp)
    end
    res
end
# @lc code=end

nums_same_consec_diff (generic function with 1 method)

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