// 101. Symmetric Tree #include #include // given 'root' of binary tree, check whether it is a mirror of itself struct TreeNode { int val; struct TreeNode *left; struct TreeNode *right; }; bool traverse(struct TreeNode *left, struct TreeNode *right) { if (left == NULL && right == NULL) return true; if (left == NULL || right == NULL) return false; if (left->val != right->val) return false; return traverse(left->left, right->right) && traverse(left->right, right->left); } bool isSymmetric(struct TreeNode *root) { if (root == NULL) return true; return traverse(root->left, root->right); }