剑指 Offer 28. 对称的二叉树

https://leetcode-cn.com/problems/dui-cheng-de-er-cha-shu-lcof/

 

 

 注意，如果左右孩子L, R数值相同，再比较这两棵子树时，要比较的是哪两对结点。

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool Comp(TreeNode* L, TreeNode* R) {
        if((L == NULL) && (R == NULL)) return true;
        if((L == NULL) && (R != NULL)) return false;
        if((L != NULL) && (R == NULL)) return false;
        if(L->val != R->val) return false;

        bool ins = Comp(L->right, R->left);
        bool outs = Comp(L->left, R->right);
        return (ins & outs);
    }

    bool isSymmetric(TreeNode* root) {
        if(root == NULL) return true;
        return Comp(root->left, root->right);
    }
};