LeetCode/cpp/numbers-with-same-consecutive-differences.cpp

#include <vector>

namespace {

void nums_same_consec_diff(int n, int k, std::vector<int> &nums, int number) {
    if (n == 0) {
        nums.push_back(number);
        return;
    }

    auto last_digit = number % 10;
    for (int d = 0; d < 10; d++) {
        if (std::abs(last_digit - d) == k) {
            nums_same_consec_diff(n - 1, k, nums, number * 10 + d);
        }
    }
}

} // namespace

class Solution {
  public:
    std::vector<int> numsSameConsecDiff(int n, int k) {
        std::vector<int> nums;

        for (int d = 1; d < 10; d++) {
            nums_same_consec_diff(n - 1, k, nums, d);
        }

        return nums;
    }
};

#pragma region tests

#include <gtest/gtest.h>

TEST(examples, first) {
    Solution s;
    ASSERT_EQ(s.numsSameConsecDiff(3, 7),
              (std::vector{181, 292, 707, 818, 929}));
}

TEST(examples, second) {
    Solution s;
    ASSERT_EQ(s.numsSameConsecDiff(2, 1),
              (std::vector{10, 12, 21, 23, 32, 34, 43, 45, 54, 56, 65, 67, 76,
                           78, 87, 89, 98}));
}

TEST(same, two) {
    Solution s;
    ASSERT_EQ(s.numsSameConsecDiff(2, 0),
              (std::vector{11, 22, 33, 44, 55, 66, 77, 88, 99}));
}

TEST(same, three) {
    Solution s;
    ASSERT_EQ(s.numsSameConsecDiff(3, 0),
              (std::vector{111, 222, 333, 444, 555, 666, 777, 888, 999}));
}

int main(int argc, char **argv) {
    ::testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}

#pragma endregion /* tests */