[LeetCode] 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.

/**
 * 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 isSymmetric(TreeNode *root) {
        if(root == NULL)
            return true;
        TreeNode *pleft = root->left;
        TreeNode *pright = root->right;
        return isMirror(pleft,pright);
        
    }
private:
    bool isMirror(TreeNode *pleft,TreeNode *pright){
        if(pleft==NULL && pright==NULL)
            return true;
        if((pleft==NULL && pright!=NULL)||(pleft!=NULL && pright==NULL))
            return false;
        else if(pleft->val != pright->val)
            return false;
        else if(isMirror(pleft->left,pright->right)==false || isMirror(pleft->right,pright->left)==false)
            return false;
        else
            return true;
    
    
    }
};