Check If binary tree is Foldable or not in C

Tree is Foldable or Not?

Here, in this page we will write a C program to check whether the given binary tree is foldable or not. A Tree is said to be foldable if its left and right counter part can be made to overlap with each other .
Foldable tree or not

Algorithm :

  • If tree is empty, then return true.
  • Convert the left subtree to its mirror image mirror(root->left); 
  • Check if the structure of left subtree and right subtree is same and store the result.
    res = isStructSame(root->left, root->right);
  • isStructSame() recursively compares structures of two subtrees and returns true if structures are same 
  • Revert the changes made in step 2 to get the original tree. mirror(root->left);
  • Return result res stored in step 2.
Foldable tree or not in C

C code based on above Algorithm

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

#define bool int
#define true 1
#define false 0

struct node {
int data;
struct node* left;
struct node* right;

void mirror(struct node* node);

bool isStructSame(struct node* a, struct node* b);

bool isFoldable(struct node* root)
bool res;

if (root == NULL)
return true;


res = isStructSame(root->left, root->right);


return res;

bool isStructSame(struct node* a, struct node* b)
if (a == NULL && b == NULL) {
return true;
if (a != NULL && b != NULL && isStructSame(a->left, b->left) && isStructSame(a->right, b->right)) {
return true;

return false;

void mirror(struct node* node)
if (node == NULL)
else {
struct node* temp;


temp = node->left;
node->left = node->right;
node->right = temp;

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

return (node);

int main(void)
struct node* root = newNode(10);
root->left = newNode(20);
root->right = newNode(30);
root->right->left = newNode(40);
root->left->right = newNode(50);

if (isFoldable(root) == 1) {
printf("\n Tree is foldable");
else {
printf("\n Tree is not foldable");

return 0;
Output :

Tree is foldable