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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