Check if There is a Valid Partition For The Array

CMakeLists.txt

@@ -76,6 +76,7 @@ add_task(check-if-array-is-sorted-and-rotated)
 add_task(check-if-it-is-a-straight-line)
 add_task(check-if-n-and-its-double-exist)
 add_task(check-if-one-string-swap-can-make-strings-equal)
+add_task(check-if-there-is-a-valid-partition-for-the-array)
 add_task(checking-existence-of-edge-length-limited-paths)
 add_task(cherry-pickup)
 add_task(cherry-pickup-ii)

solutions/check-if-there-is-a-valid-partition-for-the-array/CMakeLists.txt

@@ -0,0 +1 @@
+add_catch(test_check_if_there_is_a_valid_partition_for_the_array test.cpp)

solutions/check-if-there-is-a-valid-partition-for-the-array/solution.hpp

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <vector>
+
+class Solution {
+public:
+  bool validPartition(const std::vector<int> &nums) {
+    const int n = nums.size();
+    switch (n) {
+    case 1:
+      return false;
+    case 2:
+      return valid2(0, nums);
+    case 3:
+      return valid3(0, nums);
+    }
+
+    auto a = false;
+    auto b = valid2(n - 2, nums);
+    auto c = valid3(n - 3, nums);
+
+    for (int i = n - 4; i >= 0; --i) {
+      const auto d = valid2(i, nums) & b | valid3(i, nums) & a;
+      a = b, b = c, c = d;
+    }
+
+    return c;
+  }
+
+private:
+  bool valid2(int i, const std::vector<int> &nums) {
+    return nums[i] == nums[i + 1];
+  }
+
+  bool valid3(int i, const std::vector<int> &nums) {
+    return nums[i] == nums[i + 1] && nums[i] == nums[i + 2] ||
+           nums[i] == nums[i + 1] - 1 && nums[i] == nums[i + 2] - 2;
+  }
+};

solutions/check-if-there-is-a-valid-partition-for-the-array/test.cpp

@@ -0,0 +1,51 @@
+#include <catch.hpp>
+
+#include <solution.hpp>
+
+TEST_CASE("Simple") {
+  {
+    std::vector<int> nums{4, 4, 4, 5, 6};
+    REQUIRE(Solution().validPartition(nums));
+  }
+  {
+    std::vector<int> nums{4, 4, 4, 10, 10, 1, 2, 3, 9, 9};
+    REQUIRE(Solution().validPartition(nums));
+  }
+  {
+    std::vector<int> nums{4, 4, 4, 10, 10, 1, 2, 3, 50, 9, 9};
+    REQUIRE_FALSE(Solution().validPartition(nums));
+  }
+  {
+    std::vector<int> nums{1, 1, 1, 2};
+    REQUIRE_FALSE(Solution().validPartition(nums));
+  }
+  {
+    std::vector<int> nums{1, 2};
+    REQUIRE_FALSE(Solution().validPartition(nums));
+  }
+  {
+    std::vector<int> nums{1};
+    REQUIRE_FALSE(Solution().validPartition(nums));
+  }
+  {
+    std::vector<int> nums{1, 1};
+    REQUIRE(Solution().validPartition(nums));
+  }
+  {
+    std::vector<int> nums{1, 2, 3};
+    REQUIRE(Solution().validPartition(nums));
+  }
+  {
+    std::vector<int> nums{1, 1, 1};
+    REQUIRE(Solution().validPartition(nums));
+  }
+  {
+    std::vector<int> nums{1, 1, 2};
+    REQUIRE_FALSE(Solution().validPartition(nums));
+  }
+  {
+    std::vector<int> nums{993335, 993336, 993337, 993338,
+                          993339, 993340, 993341};
+    REQUIRE_FALSE(Solution().validPartition(nums));
+  }
+}