solve.c

#include <stdio.h>
#include <stdbool.h>
#include <assert.h>
#include <stdlib.h>
struct TreeNode {
	int val;
	struct TreeNode *left;
	struct TreeNode *right;
};
bool isLeftRightSymmetric(struct TreeNode *left, struct TreeNode *right)
{
	if (left == NULL)
		return right == NULL;
	if (right == NULL)
		return false;
	return left->val == right->val
		&& isLeftRightSymmetric(left->left, right->right)
		&& isLeftRightSymmetric(left->right,right->left);
}
bool isSymmetric(struct TreeNode *root) {
	if (root == NULL)
		return true;
	return isLeftRightSymmetric(root->left, root->right);
}
struct TreeNode *mk_node(int val)
{
	struct TreeNode *p = malloc(sizeof(*p));
	p->val = val;
	p->left = p->right = NULL;
	return p;
}
struct TreeNode* mk_children(struct TreeNode *root, int left, int right)
{
	assert(root != NULL);
	root -> left = mk_node(left);
	root -> right = mk_node(right);
	return root;
}
int main(int argc, char **argv)
{
	struct TreeNode *root = mk_node(1);
	mk_children(root, 2, 2);
	mk_children(root->left, 3, 4);
	mk_children(root->right, 4, 3);
	printf("%d\n", isSymmetric(root));
	return 0;
}