Add binary tree problems from Leetcode

Author: padth4i

Tree/(LEETCODE) BinaryTreeInorderTraversal.cpp

@@ -0,0 +1,30 @@
+/**
+
+Given the root of a binary tree, return the inorder traversal of its nodes' values.
+
+ * Definition for a binary tree node.
+ * 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<int> inorderTraversal(TreeNode* root) {
+        vector<int> inorder;
+        inorderTraversal(root, inorder);
+        return inorder;
+    }
+    
+    void inorderTraversal(TreeNode* root, vector<int> &inorder) {
+        if (!root)
+            return;
+        inorderTraversal(root->left, inorder);
+        inorder.push_back(root->val);
+        inorderTraversal(root->right, inorder);
+    }
+};

Tree/(LEETCODE) SameTree.cpp

@@ -0,0 +1,29 @@
+/**
+
+Given the roots of two binary trees p and q, write a function to check if they are the same or not.
+
+Two binary trees are considered the same if they are structurally identical, and the nodes have the same value.
+
+ * Definition for a binary tree node.
+ * 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:
+    bool isSameTree(TreeNode* p, TreeNode* q) {
+        if (p == NULL && q == NULL)
+            return true;
+        if (p == NULL || q == NULL)
+            return false;
+        if (p->val == q->val) {
+            return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
+        }
+        return false;
+    }
+};

Tree/(LEETCODE) SymmetricTree.cpp

@@ -0,0 +1,34 @@
+/**
+
+Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).
+
+ * Definition for a binary tree node.
+ * 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:
+    bool isSymmetric(TreeNode* root) {
+        if (root == NULL)
+            return true;
+        return isSymmetric(root->left, root->right);
+    }
+    
+    bool isSymmetric(TreeNode* p, TreeNode* q) {
+        if (p == NULL && q == NULL)
+            return true;
+        if (p == NULL || q == NULL)
+            return false;
+        
+        if (p->val == q->val) {
+            return isSymmetric(p->left, q->right) && isSymmetric(p->right, q->left);
+        }
+        return false;
+    }
+};