day 18: 102-binary-tree-level-order-traversal

102-binary-tree-level-order-traversal/driver.cpp

@@ -0,0 +1,15 @@
+#include "soln.hpp"
+
+int main()
+{
+	TreeNode n7 = TreeNode(7);
+	TreeNode n15 = TreeNode(15);
+	TreeNode n20 = TreeNode(20, &n15, &n7);
+	TreeNode n5 = TreeNode(5);
+	TreeNode n9 = TreeNode(9, &n5, nullptr);
+	TreeNode n3 = TreeNode(3, &n9, &n20);
+	vector<vector<int>> answer = {{3}, {9, 20}, {5, 15, 7}};
+	Solution soln;
+	cout << "Level-order traversal correct? " << soln.test(&n3, answer) << endl;
+	return 0;
+}

102-binary-tree-level-order-traversal/soln.cpp

@@ -0,0 +1,42 @@
+#include "soln.hpp"
+
+vector<vector<int>> Solution::levelOrder(TreeNode *root)
+{
+	vector<TreeNode *> tree_queue;
+	vector<vector<int>> traversal;
+	if (root == nullptr)
+	{
+		return traversal;
+	}
+	TreeNode *current = root;
+	tree_queue.push_back(current);
+	while (!tree_queue.empty())
+	{
+		traversal.push_back(vector<int>());
+		for (auto node : tree_queue)
+		{
+			if (node != nullptr)
+			{
+				traversal.back().push_back(node->val);
+			}
+		}
+		int level_size = tree_queue.size();
+		for (int i = 0; i < level_size; i++)
+		{
+			if (tree_queue[0] != nullptr)
+			{
+				if (tree_queue[0]->left)
+					tree_queue.push_back(tree_queue[0]->left);
+				if (tree_queue[0]->right)
+					tree_queue.push_back(tree_queue[0]->right);
+			}
+			tree_queue.erase(tree_queue.begin());
+		}
+	}
+	return traversal;
+}
+
+bool Solution::test(TreeNode *root, vector<vector<int>> answer)
+{
+	return levelOrder(root) == answer;
+}

102-binary-tree-level-order-traversal/soln.hpp

@@ -0,0 +1,17 @@
+#include <bits/stdc++.h>
+using namespace std;
+struct TreeNode
+{
+	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 Solution
+{
+public:
+	vector<vector<int>> levelOrder(TreeNode *root);
+	bool test(TreeNode *root, vector<vector<int>> answer);
+};