1457. Pseudo-Palindromic Paths in a Binary Tree | Leetcode solution

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 1457. Pseudo-Palindromic Paths in a Binary Tree

Given a binary tree where node values are digits from 1 to 9. A path in the binary tree is said to be pseudo-palindromic if at least one permutation of the node values in the path is a palindrome.

Return the number of pseudo-palindromic paths going from the root node to leaf nodes.

 

Example 1:

Input: root = [2,3,1,3,1,null,1]
Output: 2 
Explanation: The figure above represents the given binary tree. There are three paths going from the root node to leaf nodes: the red path [2,3,3], the green path [2,1,1], and the path [2,3,1]. Among these paths only red path and green path are pseudo-palindromic paths since the red path [2,3,3] can be rearranged in [3,2,3] (palindrome) and the green path [2,1,1] can be rearranged in [1,2,1] (palindrome).

Example 2:

Input: root = [2,1,1,1,3,null,null,null,null,null,1]
Output: 1 
Explanation: The figure above represents the given binary tree. There are three paths going from the root node to leaf nodes: the green path [2,1,1], the path [2,1,3,1], and the path [2,1]. Among these paths only the green path is pseudo-palindromic since [2,1,1] can be rearranged in [1,2,1] (palindrome).

Example 3:

Input: root = [9]
Output: 1

 

Constraints:

  • The number of nodes in the tree is in the range [1, 105].
  • 1 <= Node.val <= 9

solution:

/**
 * 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:
    void paths(TreeNode * root , vector<int>t ,int &count )
    {
         if(root->left == NULL && root->right == NULL)
         { 
            t[root->val]++;
            int g = 0;
            int flag = 0;
            for(int i = 0 ; i <10 ; i++)
            {    
                if(t[i] %2 != 0)
                {
                    if(flag != 1)
                        flag =1;
                    else
                    {   
                        g =1 ;
                        break;
                    }
                }

            }
            if(g == 0)
               count++;
           return;
         }
         
        if(root->left != NULL)
        {   
            t[root->val]++;
            paths(root->left, t, count );
            t[root->val]--;
        }
        if(root->right != NULL)
        {   
            t[root->val]++;
            paths(root->right, t , count);
            t[root->val]--;
        }
             
    }
    int pseudoPalindromicPaths (TreeNode* root) {
        
         vector<int>t(10, 0);
        int count = 0;
        paths(root , t, count);
        
        
        return count;
        
    }
};





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