1609. Even Odd Tree.cpp

A binary tree is named Even-Odd if it meets the following conditions:

The root of the binary tree is at level index 0, its children are at level index 1, their children are at level index 2, etc.
For every even-indexed level, all nodes at the level have odd integer values in strictly increasing order (from left to right).
For every odd-indexed level, all nodes at the level have even integer values in strictly decreasing order (from left to right).
Given the root of a binary tree, return true if the binary tree is Even-Odd, otherwise return false.



Example 1:



Input: root = [1,10,4,3,null,7,9,12,8,6,null,null,2]
Output: true
Explanation: The node values on each level are:
Level 0: [1]
Level 1: [10,4]
Level 2: [3,7,9]
Level 3: [12,8,6,2]
Since levels 0 and 2 are all odd and increasing, and levels 1 and 3 are all even and decreasing, the tree is Even-Odd.
Example 2:



Input: root = [5,4,2,3,3,7]
Output: false
Explanation: The node values on each level are:
Level 0: [5]
Level 1: [4,2]
Level 2: [3,3,7]
Node values in the level 2 must be in strictly increasing order, so the tree is not Even-Odd.
Example 3:



Input: root = [5,9,1,3,5,7]
Output: false
Explanation: Node values in the level 1 should be even integers.
Example 4:

Input: root = [1]
Output: true
Example 5:

Input: root = [11,8,6,1,3,9,11,30,20,18,16,12,10,4,2,17]
Output: true


Constraints:

The number of nodes in the tree is in the range [1, 105].
1 <= Node.val <= 106






/**
 * 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 check(vector<TreeNode*> v, int index){
        int n=v.size();

        //for(int i=0;i<n;i++) cout<<v[i]->val<<" "; cout<<endl;


        if(index%2==0){
            if(v[0]->val%2==0 || v[n-1]->val%2==0) return false;
            for(int i=0;i<n-1;i++){
                if(v[i]->val%2==0 || v[i]->val>=v[i+1]->val) return false;
            }
        } else {
            if(v[0]->val%2!=0 || v[n-1]->val%2!=0) return false;
            for(int i=0;i<n-1;i++){
                if(v[i]->val%2!=0 || v[i]->val<=v[i+1]->val) return false;
            }
        }

        return true;
    }


    bool isEvenOddTree(TreeNode* root) {
        queue<TreeNode*> q;

        q.push(root);

        int index=0;

        while(!q.empty()){
            int size=q.size();


            vector<TreeNode*>v;
            while(!q.empty()){
                v.push_back(q.front());
                q.pop();
            }

            for(auto &x: v) q.push(x);

            if(!check(v, index)) return false;

            while(size--){
                TreeNode *curr=q.front();
                if(curr->left) q.push(curr->left);
                if(curr->right) q.push(curr->right);
                q.pop();
            }
            index++;
        }

        return true;
    }
};