Check whether tree is Symmetric in C

March 19, 2025

Tree is Symmetric or Not?

Here, in this page we will discuss a C program to check whether a tree is Symmetric (mirror of itself) or not.

We need to write a recursive function isSymmetrical() that takes two trees as argument and returns true if trees are Symmetrical and false if trees are not Symmetrical.

symmetric tree or not in C

Check Whether Tree is Symmetric in C Language

Algorithm :

  • Create a recursive function isMirror() that takes two trees as an argument and returns 1 if trees are the mirrored and 0 if trees are not mirrored.
  • The isSMirror() function recursively checks two roots and subtrees under the root.
  • And isSymmetric() takes the root of the binary tree as an parameter and then will return true is isMirror() returns 1, otherwise it return 1.
  • If isSymmetric() returns 1 it means that given tree is symmetric, otherwise not  symmetric.

Check whether two tree are identical

Spiral Order traversal of Tree

Check If binary tree if Foldable or not

Sum of all nodes in Binary Tree

Check for Children-Sum in Binary Tree

Code in C based on above approach

Run 
#include <stdio.h>
#include <stdlib.h>

struct Node
{
int key;
struct Node* left;
struct Node* right;
};

struct Node* newNode(int data)
{
struct Node* node = (struct Node*)
malloc(sizeof(struct Node));
node->key = data;
node->left = NULL;
node->right = NULL;

return(node);
}

int isMirror(struct Node* root1, struct Node* root2)
{

if (root1 == NULL && root2 == NULL)
return 1;

if (root1 && root2 && root1->key == root2->key)
return isMirror(root1->left, root2->right) && isMirror(root1->right, root2->left);

return 0;
}

int isSymmetric(struct Node* root)
{
return isMirror(root, root);
}

int main()
{
struct 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))
printf("Symmetric");
else
printf("Not symmetric");
return 0;
}

Output:

Symmetric