leetcode 101. Symmetric Tree

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree is symmetric:

1
/ \
2   2
/ \ / \
3  4 4  3

But the following is not:

1
/ \
2   2
\   \
3    3

Note:
Bonus points if you could solve it both recursively and iteratively.

[Solution]

递归判断

symCheck(left->left, right->right) && symCheck(left->right, right->left)

bool isSymmetric(TreeNode *root)
{
if (root == NULL)
return true;
return symCheck(root->left, root->right);
}

bool symCheck(TreeNode *left, TreeNode *right)
{
if (left == NULL || right == NULL)
{
if (left == right)
return true;
else
return fasle;
}

if (left->val == right->val)
return symCheck(left->left, right->right) && symCheck(left->right, right->left);
else
return false;
}