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.

鏡面，左對右 ， 右對左

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isSame(TreeNode* rootLeft, TreeNode* rootRight)
    {
        if(rootLeft == NULL && rootRight == NULL)
            return true;
        else if(rootLeft != NULL && rootRight != NULL)
        {
            if(rootLeft->val != rootRight->val)
                return false;
            return isSame(rootLeft->left, rootRight->right) &&
             isSame(rootLeft->right, rootRight->left);
        }
        return false;
    }
    bool isSymmetric(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if(root)
        {
            return isSame(root->left, root->right);
        }
        return true;
    }
};