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Find the node whose xor with x gives minimum value
  • Difficulty Level : Medium
  • Last Updated : 16 Apr, 2021

Given a tree, and the weights of all the nodes and an integer x, the task is to find a node i such that weight[i] xor x is minimum.
Examples: 
 

Input: 
 

x = 15 
Output:
Node 1: 5 xor 15 = 10 
Node 2: 10 xor 15 = 5 
Node 3: 11 xor 15 = 4 
Node 4: 8 xor 15 = 7 
Node 5: 6 xor 15 = 9 
 

 



Approach: Perform dfs on the tree and keep track of the node whose weighted xor with x gives the minimum value.
Below is the implementation of above approach:
 

C++




// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
 
int minimum = INT_MAX, x, ans;
 
vector<int> graph[100];
vector<int> weight(100);
 
// Function to perform dfs to find
// the minimum xored value
void dfs(int node, int parent)
{
    // If current value is less than
    // the current minimum
    if (minimum > (weight[node] ^ x)) {
        minimum = weight[node] ^ x;
        ans = node;
    }
    for (int to : graph[node]) {
        if (to == parent)
            continue;
        dfs(to, node);
    }
}
 
// Driver code
int main()
{
    x = 15;
 
    // Weights of the node
    weight[1] = 5;
    weight[2] = 10;
    weight[3] = 11;
    weight[4] = 8;
    weight[5] = 6;
 
    // 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 << ans;
 
    return 0;
}

Java




// Java implementation of the approach
import java.util.*;
import java.lang.*;
 
class GFG
{
 
    static int minimum = Integer.MAX_VALUE, x, ans;
 
    @SuppressWarnings("unchecked")
    static Vector<Integer>[] graph = new Vector[100];
    static int[] weight = new int[100];
 
    // This block is executed even before main() function
    // This is necessary otherwise this program will
    // throw "NullPointerException"
    static
    {
        for (int i = 0; i < 100; i++)
            graph[i] = new Vector<>();
    }
 
    // Function to perform dfs to find
    // the minimum xored value
    static void dfs(int node, int parent)
    {
 
        // If current value is less than
        // the current minimum
        if (minimum > (weight[node] ^ x))
        {
            minimum = weight[node] ^ x;
            ans = node;
        }
        for (int to : graph[node])
        {
            if (to == parent)
                continue;
            dfs(to, node);
        }
    }
 
    // Driver Code
    public static void main(String[] args)
    {
        x = 15;
 
        // Weights of the node
        weight[1] = 5;
        weight[2] = 10;
        weight[3] = 11;
        weight[4] = 8;
        weight[5] = 6;
 
        // Edges of the tree
        graph[1].add(2);
        graph[2].add(3);
        graph[2].add(4);
        graph[1].add(5);
 
        dfs(1, 1);
 
        System.out.println(ans);
    }
}
 
// This code is contributed by SHUBHAMSINGH10

C#




// C# implementation of the approach
using System;
using System.Collections.Generic;
 
class GFG
{
 
static int minimum = int.MaxValue, x, ans;
 
static List<List<int>> graph = new List<List<int>>();
static List<int> weight = new List<int>();
 
 
// Function to perform dfs to find
// the minimum value
static void dfs(int node, int parent)
{
    // If current value is less than
    // the current minimum
    if (minimum > (weight[node] ^ x))
    {
        minimum = weight[node] ^ x;
        ans = node;
    }
         
    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()
{
    x = 15;
 
    // Weights of the node
    weight.Add(0);
    weight.Add(5);
    weight.Add(10);
    weight.Add(11);;
    weight.Add(8);
    weight.Add(6);
     
    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.Write( ans);
}
}
 
// This code is contributed by SHUBHAMSINGH10

Python3




# Python implementation of the approach
from sys import maxsize
 
minimum, x, ans = maxsize, None, None
 
graph = [[] for i in range(100)]
weight = [0] * 100
 
# Function to perform dfs to find
# the minimum xored value
def dfs(node, parent):
    global x, ans, graph, weight, minimum
 
    # If current value is less than
    # the current minimum
    if minimum > weight[node] ^ x:
        minimum = weight[node] ^ x
        ans = node
 
    for to in graph[node]:
        if to == parent:
            continue
        dfs(to, node)
 
# Driver Code
if __name__ == "__main__":
 
    x = 15
 
    # Weights of the node
    weight[1] = 5
    weight[2] = 10
    weight[3] = 11
    weight[4] = 8
    weight[5] = 6
 
    # Edges of the tree
    graph[1].append(2)
    graph[2].append(3)
    graph[2].append(4)
    graph[1].append(5)
 
    dfs(1, 1)
 
    print(ans)
 
# This code is contributed by
# sanjeev2552

Javascript




<script>
// Javascript implementation of the approach
      
    let minimum = Number.MAX_VALUE, x, ans;
    let graph = new Array(100);
    let weight = new Array(100);
    for(let i = 0; i < 100; i++)
    {
        graph[i] = [];
        weight[i] = 0;
    }
     
    // Function to perform dfs to find
    // the minimum xored value
    function  dfs(node, parent)
    {
     
        // If current value is less than
        // the current minimum
        if (minimum > (weight[node] ^ x))
        {
            minimum = weight[node] ^ x;
            ans = node;
        }
        for (let to = 0; to < graph[node].length; to++)
        {
            if (graph[node][to] == parent)
                continue;
            dfs(graph[node][to], node);
        }
    }
     
    // Driver Code
    x = 15;
     
   // Weights of the node
    weight[1] = 5;
    weight[2] = 10;
    weight[3] = 11;
    weight[4] = 8;
    weight[5] = 6;
 
    // Edges of the tree
    graph[1].push(2);
    graph[2].push(3);
    graph[2].push(4);
    graph[1].push(5);
 
    dfs(1, 1);
    document.write(ans);
     
    // This code is contributed by unknown2108
</script>
Output: 
3

 

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