Count the nodes of the given tree whose weighted string is a palindrome
Given a tree, and the weights (in the form of strings) of all the nodes, the task is to count the nodes whose weights are palindrome.
Examples:
Input:Output: 3 Only the weights of the nodes 2, 3 and 5 are palindromes.
Approach: Perform dfs on the tree and for every node, check if it’s string is palindrome or not. If yes then increment the count.
Implementation:
C++
// C++ implementation of the approach #include <bits/stdc++.h> using namespace std; int cnt = 0; vector< int > graph[100]; vector<string> weight(100); // Function that returns true // if x is a palindrome bool isPalindrome(string x) { int n = x.size(); for ( int i = 0; i < n / 2; i++) { if (x[i] != x[n - 1 - i]) return false ; } return true ; } // Function to perform dfs void dfs( int node, int parent) { // Weight of the current node string x = weight[node]; // If the weight is a palindrome if (isPalindrome(x)) cnt += 1; for ( int to : graph[node]) { if (to == parent) continue ; dfs(to, node); } } // Driver code int main() { // Weights of the node weight[1] = "abc" ; weight[2] = "aba" ; weight[3] = "bcb" ; weight[4] = "moh" ; weight[5] = "aa" ; // Edges of the tree graph[1].push_back(2); graph[2].push_back(3); graph[2].push_back(4); graph[1].push_back(5); dfs(1, 1); cout << cnt; return 0; } |
Java
// Java implementation of the approach import java.util.*; class GFG { static int cnt = 0 ; static Vector<Vector<Integer>> graph = new Vector<Vector<Integer>>(); static Vector<String> weight = new Vector<String>(); // Function that returns true // if x is a palindrome static boolean isPalindrome(String x) { int n = x.length(); for ( int i = 0 ; i < n / 2 ; i++) { if (x.charAt(i) != x.charAt(n - 1 - i)) return false ; } return true ; } // Function to perform dfs static void dfs( int node, int parent) { // Weight of the current node String x = weight.get(node); // If the weight is a palindrome if (isPalindrome(x)) cnt += 1 ; for ( int i= 0 ;i<graph.get(node).size();i++) { if ( graph.get(node).get(i)== parent) continue ; dfs(graph.get(node).get(i), node); } } // Driver code public static void main(String args[]) { // Weights of the node weight.add( "" ); weight.add( "abc" ); weight.add( "aba" ); weight.add( "bcb" ); weight.add( "moh" ); weight.add( "aa" ); for ( int i = 0 ; i < 100 ; i++) graph.add( new Vector<Integer>()); // Edges of the tree graph.get( 1 ).add( 2 ); graph.get( 2 ).add( 3 ); graph.get( 2 ).add( 4 ); graph.get( 1 ).add( 5 ); dfs( 1 , 1 ); System.out.println( cnt); } } // This code is contributed by Arnab Kundu |
Python3
# Python3 implementation of the approach cnt = 0 graph = [ 0 ] * 100 for i in range ( 100 ): graph[i] = [] weight = [ "0" ] * 100 # Function that returns true # if x is a palindrome def isPalindrome(x): n = len (x) for i in range ( 0 , n / / 2 ): if x[i] ! = x[n - 1 - i]: return False return True # Function to perform dfs def dfs(node, parent): global cnt # Weight of the current node x = weight[node] # If the weight is a palindrome if (isPalindrome(x)): cnt + = 1 for to in graph[node]: if to = = parent: continue dfs(to, node) # Driver Code if __name__ = = "__main__" : # Weights of the node weight[ 0 ] = "" weight[ 1 ] = "abc" weight[ 2 ] = "aba" weight[ 3 ] = "bcb" weight[ 4 ] = "moh" weight[ 5 ] = "aa" # Edges of the tree graph[ 1 ].append( 2 ) graph[ 2 ].append( 3 ) graph[ 2 ].append( 4 ) graph[ 1 ].append( 5 ) dfs( 1 , 1 ) print (cnt) # This code is contributed by # sanjeev2552 |
C#
// C# implementation of the approach using System; using System.Collections.Generic; class GFG { static int cnt = 0; static List<List< int >> graph = new List<List< int >>(); static List<String> weight = new List<String>(); // Function that returns true // if x is a palindrome static bool isPalindrome( string x) { int n = x.Length; for ( int i = 0; i < n / 2; i++) { if (x[i] != x[n - 1 - i]) return false ; } return true ; } // Function to perform dfs static void dfs( int node, int parent) { // Weight of the current node String x = weight[node]; // If the weight is a palindrome if (isPalindrome(x)) cnt += 1; for ( int i = 0; i < graph[node].Count; i++) { if (graph[node][i] == parent) continue ; dfs(graph[node][i], node); } } // Driver code public static void Main(String []args) { // Weights of the node weight.Add( "" ); weight.Add( "abc" ); weight.Add( "aba" ); weight.Add( "bcb" ); weight.Add( "moh" ); weight.Add( "aa" ); for ( int i = 0; i < 100; i++) graph.Add( new List< int >()); // Edges of the tree graph[1].Add(2); graph[2].Add(3); graph[2].Add(4); graph[1].Add(5); dfs(1, 1); Console.WriteLine( cnt); } } // This code has been contributed by 29AjayKumar |
Output:
3
Complexity Analysis:
- Time Complexity: O(N*Len) where Len is the maximum length of the weighted string of a node in the given tree.
In DFS, every node of the tree is processed once and hence the complexity due to the DFS is O(N) for N nodes in the tree. Also, processing of every node involves traversing the weighted string of that node once, thus adding a complexity of O(Len) where Len is the length of the weighted string. Therefore, the total time complexity is O(N*Len). - Auxiliary Space: O(1).
Any extra space is not required, so the space complexity is constant.
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