Added Count Complete Tree Nodes

CMakeLists.txt

@@ -821,4 +821,15 @@ add_executable(PathSum
 target_link_libraries(
         PathSum
         GTest::gtest_main
+)
+
+# Count Complete Tree Nodes
+add_executable(CountCompleteTreeNodes
+        Easy/CountCompleteTreeNodes/include/solution.hpp
+        Easy/CountCompleteTreeNodes/tests/test.cpp
+)
+
+target_link_libraries(
+        CountCompleteTreeNodes
+        GTest::gtest_main
 )

Easy/CountCompleteTreeNodes/include/solution.hpp

@@ -0,0 +1,33 @@
+#pragma once
+
+#include <vector>
+#include <iostream>
+#include <algorithm>
+#include <gtest/gtest.h>
+
+struct TreeNode {
+    const int32_t value;
+    TreeNode *left;
+    TreeNode *right;
+    explicit TreeNode(int32_t value) :
+        value(value), left(nullptr), right(nullptr) { }
+};
+
+class Solution {
+public:
+    static auto count_nodes(TreeNode *root) -> int32_t {
+        if (root == nullptr) return 0;
+
+        int32_t count = 0;
+        std::function<void(TreeNode*)> preorder =
+                [&](TreeNode *root) -> void {
+            if (root == nullptr) return;
+            ++count;
+            preorder(root->left);
+            preorder(root->right);
+        };
+
+        preorder(root);
+        return count;
+    }
+};

Easy/CountCompleteTreeNodes/tests/test.cpp

@@ -0,0 +1,14 @@
+#include "../include/solution.hpp"
+
+auto main() -> int {
+    auto *root = new TreeNode(1);
+    root->left = new TreeNode(2);
+    root->left->left = new TreeNode(4);
+    root->left->right = new TreeNode(5);
+    root->right = new TreeNode(3);
+    root->right->left = new TreeNode(6);
+
+    std::cout << Solution::count_nodes(root);
+
+    return 0;
+}