Check for Symmetric tree in Binary Tree in C++

CPP/Symmetric_Tree.cpp

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+// C++ program to check if a given Binary
+// Tree is symmetric or not
+#include<bits/stdc++.h>
+using namespace std;
+
+// A Binary Tree Node
+struct Node
+{
+    int key;
+    struct Node* left, *right;
+};
+
+// Utility function to create new Node
+Node *newNode(int key)
+{
+    Node *temp = new Node;
+    temp->key = key;
+    temp->left = temp->right = NULL;
+    return (temp);
+}
+
+// Returns true if a tree is symmetric
+// i.e. mirror image of itself
+bool isSymmetric(struct Node* root)
+{
+    if(root == NULL)
+        return true;
+
+    // If it is a single tree node, then
+    // it is a symmetric tree.
+    if(!root->left && !root->right)
+        return true;
+
+    queue <Node*> q;
+
+    q.push(root);
+
+    if(root->left && root->right)   	//As root is not in pair ,
+        {								//so we adjust the left and right child of root
+            q.push(root->left);     	//by pushing into the queue and we make sure to
+            q.push(root->right);		//pop the root element here.
+            q.pop();
+        }
+     else if(root->left || root->right) //If any child of the root is Null
+            return false;				//we return false.
+
+    // To store two nodes for checking their
+    // symmetry.
+    Node* leftNode, *rightNode;
+
+    while(!q.empty()){
+
+        // Remove first two nodes to check
+        // their symmetry.
+        leftNode = q.front();
+        q.pop();
+
+        rightNode = q.front();
+        q.pop();
+
+        // if both left and right nodes
+        // exist, but have different
+        // values--> inequality, return false
+          if(leftNode->key != rightNode->key)
+          {
+          return false;
+          }
+
+          // Push left child of left subtree node
+          // and right child of right subtree
+          // node in queue.
+          if(leftNode->left && rightNode->right)
+          {
+              q.push(leftNode->left);
+              q.push(rightNode->right);
+          }
+
+          // If only one child is present alone
+          // and other is NULL, then tree
+          // is not symmetric.
+          else if (leftNode->left || rightNode->right)
+          return false;
+
+          // Push right child of left subtree node
+          // and left child of right subtree node
+          // in queue.
+          if(leftNode->right && rightNode->left)
+          {
+              q.push(leftNode->right);
+              q.push(rightNode->left);
+          }
+
+          // If only one child is present alone
+          // and other is NULL, then tree
+          // is not symmetric.
+          else if(leftNode->right || rightNode->left)
+          return false;
+    }
+
+    return true;
+}
+
+// Driver program
+int main()
+{
+    // Let us construct the Tree shown in
+    // the above figure
+    Node *root = newNode(1);
+    root->left = newNode(2);
+    root->right = newNode(2);
+    root->left->left = newNode(3);
+    root->left->right = newNode(4);
+    root->right->left = newNode(4);
+    root->right->right = newNode(3);
+
+    if(isSymmetric(root))
+        cout << "The given tree is Symmetric";
+    else
+        cout << "The given tree is not Symmetric";
+    return 0;
+}
+
+// This code is contributed by Tanya Srivastava