对称的二叉树

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};
*/
class Solution {
public:
    bool isSymmetrical(TreeNode* pRoot)
    {
    	if(pRoot==NULL)	return true;
        TreeNode * pRight=pRoot->right;
        TreeNode * pLeft=pRoot->left;
        if(pRight==NULL && pLeft==NULL)	return true;
        if(pRight==NULL || pLeft==NULL)	return false;
        return f(pRight,pLeft);
        
    }
    
    bool f(TreeNode * pLroot,TreeNode * pRroot) {
        if(pLroot==NULL && pRroot==NULL)	return true;
        if(pLroot==NULL || pRroot==NULL)	return false;
        if(pLroot->val!=pRroot->val)	return false;
        
        TreeNode * pL1=pLroot->left;
        TreeNode * pL2=pLroot->right;
        
        TreeNode * pR1=pRroot->left;
        TreeNode * pR2=pRroot->right;
    	
        return f(pL1,pR2)&&f(pL2,pR1);
    }

};