等价二叉树

class Solution {public:    /**     * @aaram a, b, the root of binary trees.     * @return true if they are identical, or false.     */     bool x;     bool trade(TreeNode *A)     {         if(A==NULL)         {             return 1;         }         else         return 0;     }     void look(TreeNode *a,TreeNode *b)     {         if(trade(a)!=trade(b))          {              x=0;              return ;          }         if(a==NULL||b==NULL)         return;         if(a->val!=b->val)         {               x=0;             return ;         }         if(trade(a->left)!=trade(b->left)||trade(a->right)!=trade(b->right))         {             x=0;             return;         }         if(a->val==b->val)         {            look(a->left,b->left);            look(a->right,b->right);         }         else         {             x=0;             return;         }     }    bool isIdentical(TreeNode* a, TreeNode* b) {        x=1;        look(a,b);                if(x==0)        return 0;        else        return 1;        // Write your code here    }};