Binary Trees With Factors

CMakeLists.txt

@@ -82,6 +82,7 @@ add_task(binary-tree-preorder-traversal)
 add_task(binary-tree-right-side-view)
 add_task(binary-tree-tilt)
 add_task(binary-tree-zigzag-level-order-traversal)
+add_task(binary-trees-with-factors)
 add_task(binary-watch)
 add_task(bitwise-and-of-numbers-range)
 add_task(bitwise-xor-of-all-pairings)

solutions/binary-trees-with-factors/CMakeLists.txt

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

solutions/binary-trees-with-factors/solution.hpp

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <algorithm>
+#include <cmath>
+#include <numeric>
+#include <vector>
+
+class Solution {
+public:
+  static constexpr int kMod = 1e9 + 7;
+
+  static int numFactoredBinaryTrees(std::vector<int> arr) {
+    std::sort(arr.begin(), arr.end());
+
+    std::unordered_map<int, int> indexes;
+    for (int i = 0; i < std::ssize(arr); ++i) {
+      indexes[arr[i]] = i;
+    }
+
+    std::vector<long long> dp(arr.size(), 1);
+    for (int i = 1; i < std::ssize(arr); ++i) {
+      for (int j = 0; j < i; ++j) {
+        if (arr[j] > std::sqrt(arr[i])) {
+          break;
+        }
+        if (arr[i] % arr[j] != 0) {
+          continue;
+        }
+        if (auto it = indexes.find(arr[i] / arr[j]); it != indexes.end()) {
+          const int k = it->second;
+          dp[i] += (k == j ? 1 : 2) * dp[j] * dp[k];
+          dp[i] %= kMod;
+        }
+      }
+    }
+
+    return std::accumulate(dp.begin(), dp.end(), 0LL) % kMod;
+  }
+};

solutions/binary-trees-with-factors/test.cpp

@@ -0,0 +1,26 @@
+#include <catch.hpp>
+
+#include <solution.hpp>
+
+TEST_CASE("Simple") {
+  struct TestCase {
+    std::vector<int> arr;
+    int expected;
+  };
+
+  std::vector<TestCase> test_cases{
+      {
+          .arr{2, 4, 5, 10},
+          .expected = 7,
+      },
+      {
+          .arr{2, 4},
+          .expected = 3,
+      },
+  };
+
+  for (const auto &[arr, expected] : test_cases) {
+    const auto actual = Solution::numFactoredBinaryTrees(arr);
+    REQUIRE(expected == actual);
+  }
+}