LeetCode 993. 二叉树的堂兄弟节点（前序遍历判断是否一个父亲+层次遍历判断是否在同一层）

二叉树的堂兄弟节点
代码有些冗余
两次遍历都是$O(n)$O(n)

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool isCousins(TreeNode* root, int x, int y) {
        if(preOrder(root,x,y)){
            return false;
        }
        return layerOrder(root,x,y);
    }

    bool layerOrder(TreeNode *root,int x,int y){
        queue<TreeNode*> q;
        q.push(root);
        int l;
        while(!q.empty()){
            int size = q.size();
            set<int> res;
            while(size--){
                TreeNode* r = q.front();
                q.pop();
                res.insert(r->val);
                if(r->left){
                    q.push(r->left);
                }
                if(r->right){
                    q.push(r->right);
                }
            }
            if(res.count(x) && res.count(y) ){
                
                return true;
            }
        }
        return false;
    }


    bool preOrder(TreeNode *root,int x,int y){
        if(!root || (!root->left && !root->right)){
            return false;
        }
        if(root->left && root->right){
            if( (root->left->val==x && root->right->val==y) ||
            ( (root->left->val==y && root->right->val==x)) ){
                return true;
            }
        }
        if(root->left && preOrder(root->left,x,y)  ){
            return true;
        }
        if(root->right && preOrder(root->right,x,y) ){
            return true;
        }
        return false;
    }    
};