POTD 2026-06-07 solved

core/core.h

@@ -1,10 +1,22 @@
 #pragma once
 #include<iostream>
 #include<vector>
+#include <queue>
 #include<string>
-
 using namespace std;
 
+class TreeNode
+{
+public:
+	int val;
+	TreeNode* left;
+	TreeNode* right;
+	TreeNode() : val(0), left(nullptr), right(nullptr) {}
+	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+	TreeNode(int x, TreeNode* left, TreeNode* right) : val(x), left(left), right(right) {}
+
+};
+
 class Core
 {
 private:
@@ -24,4 +36,49 @@ class Core
 			}
 		}
 	}
+
+    static void printBinaryTreeInLevelOrder(TreeNode* root)
+    {
+        if (!root)
+        {
+            cout << "\n";
+            return;
+        }
+
+        queue<TreeNode*> q;
+        q.push(root);
+        vector<string> result;
+
+        // Standard BFS Traversal
+        while (!q.empty())
+        {
+            TreeNode* current = q.front();
+            q.pop();
+
+            if (current)
+            {
+                result.push_back(to_string(current->val));
+                // Push children even if they are null (clean trailing nulls later)
+                q.push(current->left);
+                q.push(current->right);
+            }
+            else
+            {
+                result.push_back("null");
+            }
+        }
+
+        // Clean up trailing "null"s to match LeetCode's compact format
+        while (!result.empty() && result.back() == "null")
+        {
+            result.pop_back();
+        }
+
+        // Print the output
+        for (int i = 0; i < result.size(); i++)
+        {
+            cout << result[i] << " ";
+        }
+        cout << "\n";
+    }
 };

src/2100-2199/2196.cpp

@@ -0,0 +1,117 @@
+/*
+Tags
+level-medium
+tree, binary-tree, hash-map,
+
+
+Problem Description
+2196. Create Binary Tree From Descriptions
+You are given a 2D integer array descriptions where descriptions[i] = [parenti, childi, isLefti] indicates that parenti is the parent of childi in a binary tree of unique values. Furthermore,
+If isLefti == 1, then childi is the left child of parenti.
+If isLefti == 0, then childi is the right child of parenti.
+Construct the binary tree described by descriptions and return its root.
+
+The test cases will be generated such that the binary tree is valid.
+
+Example 1:
+Input: descriptions = [[20,15,1],[20,17,0],[50,20,1],[50,80,0],[80,19,1]]
+Output: [50,20,80,15,17,19]
+Explanation: The root node is the node with value 50 since it has no parent.
+The resulting binary tree is shown in the diagram.
+
+Example 2:
+Input: descriptions = [[1,2,1],[2,3,0],[3,4,1]]
+Output: [1,2,null,null,3,4]
+Explanation: The root node is the node with value 1 since it has no parent.
+The resulting binary tree is shown in the diagram.
+
+Constraints:
+1 <= descriptions.length <= 10^4
+descriptions[i].length == 3
+1 <= parenti, childi <= 10^5
+0 <= isLefti <= 1
+The binary tree described by descriptions is valid.
+
+*/
+
+#include <iostream>
+#include <vector>
+#include <string>
+#include <algorithm>
+#include <numeric>
+#include <cmath>
+#include <queue>
+#include <stack>
+#include <set>
+#include <map>
+#include <unordered_map>
+#include <unordered_set>
+#include <sstream>
+#include <limits>
+#include <iomanip>
+#include <functional>
+#include <cstring>
+#include <climits>
+#include "../../core/core.h"
+using namespace std;
+
+class Solution {
+private:
+	unordered_map<int, TreeNode*> nodeMap;
+	unordered_set<int> childSet;
+public:
+	TreeNode* createBinaryTree(vector<vector<int>>& descriptions) {
+		for (auto& it : descriptions)
+		{
+			int parent = it[0];
+			int child = it[1];
+			bool isLeft = it[2];
+			if (nodeMap.find(parent) == nodeMap.end())
+			{
+				nodeMap[parent] = new TreeNode(parent);
+			}
+			if (nodeMap.find(child) == nodeMap.end())
+			{
+				nodeMap[child] = new TreeNode(child);
+			}
+			if (isLeft)
+			{
+				nodeMap[parent]->left = nodeMap[child];
+			}
+			else
+			{
+				nodeMap[parent]->right = nodeMap[child];
+			}
+			childSet.insert(child);
+		}
+
+		for (auto& it : nodeMap)
+		{
+			auto& val = it.first;
+			auto& node = it.second;
+			if (childSet.find(val) == childSet.end())
+			{
+				return node;
+			}
+		}
+
+		return nullptr;
+	}
+};
+
+int main()
+{
+	int n;
+	Solution sol;
+	vector<vector<int>> description;
+	cin >> n;
+	for (int i = 0; i < n; i++)
+	{
+		int parent, child, isLeft;
+		cin >> parent >> child >> isLeft;
+		description.push_back({parent, child, isLeft});
+	}
+	TreeNode* root = sol.createBinaryTree(description);
+	Core::printBinaryTreeInLevelOrder(root);
+	return 0;
+}

tests/2100-2199/2196.txt

@@ -0,0 +1,19 @@
+Test Case 1:
+Input:
+5
+20 15 1
+20 17 0
+50 20 1
+50 80 0
+80 19 1
+Output:
+50 20 80 15 17 19
+
+Test Case 2:
+Input:
+3
+1 2 1
+2 3 0
+3 4 1
+Output:
+1 2 null null 3 4