Symmetric Tree

/**
 * 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 isM(TreeNode *p,TreeNode *q)
    {
        if((p->left!=NULL)^(q->right!=NULL))
            return false;
        if((p->right!=NULL)^(q->left!=NULL))
            return false;
        if(p->val!=q->val)
            return false;
        if(p->left!=NULL&&(isM(p->left,q->right)==false))
            return false;
        if((p->right!=NULL)&&(isM(p->right,q->left)==false))
            return false;
        return true;
    }
    bool isSymmetric(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if(root==NULL)
            return true;
        if(!(root->left||root->right))
            return true;
        if((root->left!=NULL)&&(root->right!=NULL))
        {
            return isM(root->left,root->right);
        }
        return false;
    }
};