cpp: add «2958. Length of Longest Subarray With at Most K Frequency»

Signed-off-by: Matej Focko <me@mfocko.xyz>

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

@@ -0,0 +1,57 @@
+#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