LeetCode/cpp/length-of-longest-subarray-with-at-most-k-frequency.cpp

#include <unordered_map>
#include <vector>

class Solution {
  public:
    int maxSubarrayLength(const std::vector<int> &nums, int k) {
        auto n = nums.size();

        std::unordered_map<int, int> freqs;
        int overshot = 0;

        std::size_t i = 0, j;
        for (j = 0; j < n; ++j) {
            ++freqs[nums[j]];

            if (freqs[nums[j]] == k + 1) {
                ++overshot;
            }

            if (overshot > 0) {
                --freqs[nums[i]];

                if (freqs[nums[i]] == k) {
                    --overshot;
                }

                ++i;
            }
        }

        return n - i;
    }
};

#ifdef _MF_TEST
#include <gtest/gtest.h>

TEST(examples, _1) {
    Solution s;
    EXPECT_EQ(s.maxSubarrayLength(std::vector{1, 2, 3, 1, 2, 3, 1, 2}, 2), 6);
}

TEST(examples, _2) {
    Solution s;
    EXPECT_EQ(s.maxSubarrayLength(std::vector{1, 2, 1, 2, 1, 2, 1, 2}, 1), 2);
}

TEST(examples, _3) {
    Solution s;
    EXPECT_EQ(s.maxSubarrayLength(std::vector{5, 5, 5, 5, 5, 5, 5}, 4), 4);
}

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