Given a** tree** with the weights of all the nodes, the task is to find the maximum weighing node whose weight has even digit sum.

**Examples:**

Input:Tree = 5 / \ 10 6 / \ 11 8Output:11Explanation:The tree node weights are: 5 -> 5 10 -> 1 + 0 = 1 6 -> 6 11 -> 1 + 1 = 2 8 -> 8 Here, digit sum for nodes containing 11, 6 and 8 are even. Hence, the maximum weighing even digit sum node is 11.Input:Tree = 1 / \ 4 7 / \ / \ 11 3 15 8Output:15Explanation:Here, digit sum for nodes containing 4, 11, 15 and 8 are even. Hence, the maximum weighing even digit sum node is 15.

**Approach:** To solve the problem mentioned above follow the steps given below:

- The idea is to perform a depth first search on the tree and for every node.
- First, find the digit sum for the weight present in the node by iterating through each digit and then check if the node has even digit sum or not.
- Finally, if it has an even digit sum then check if this node is the maximum even digit sum node we have found so far, if yes, then make this node the maximum even digit sum node.

Below is the implementation of the above approach:

## C++

`// C++ program to find the` `// maximum weighing node` `// in the tree whose weight` `// has an Even Digit Sum` `#include <bits/stdc++.h>` `using` `namespace` `std;` `const` `int` `sz = 1e5;` `int` `ans = -1;` `vector<` `int` `> graph[100];` `vector<` `int` `> weight(100);` `// Function to find the digit sum` `// for a number` `int` `digitSum(` `int` `num)` `{` ` ` `int` `sum = 0;` ` ` `while` `(num) ` ` ` `{` ` ` `sum += (num % 10);` ` ` `num /= 10;` ` ` `}` ` ` `return` `sum;` `}` `// Function to perform dfs` `void` `dfs(` `int` `node, ` `int` `parent)` `{` ` ` `// Check if the digit sum` ` ` `// of the node weight` ` ` `// is even or not` ` ` `if` `(!(digitSum(weight[node]) & 1))` ` ` `ans = max(ans, weight[node]);` ` ` `// Performing DFS to iterate the` ` ` `// remaining nodes` ` ` `for` `(` `int` `to : graph[node]) {` ` ` `if` `(to == parent)` ` ` `continue` `;` ` ` `dfs(to, node);` ` ` `}` `}` `// Driver code` `int` `main()` `{` ` ` `// 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);` ` ` `// Call the dfs function to` ` ` `// traverse through the tree` ` ` `dfs(1, 1);` ` ` `cout << ans << endl;` ` ` `return` `0;` `}` |

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## Java

`// Java program to find the` `// maximum weighing node` `// in the tree whose weight` `// has an Even Digit Sum` `import` `java.util.*;` `class` `GFG ` `{` ` ` `static` `int` `sz = (` `int` `)1e5;` ` ` `static` `int` `ans = -` `1` `;` ` ` `static` `Vector<Integer>[] graph = ` `new` `Vector[` `100` `];` ` ` `static` `int` `[] weight = ` `new` `int` `[` `100` `];` ` ` `// Function to find the digit sum` ` ` `// for a number` ` ` `static` `int` `digitSum(` `int` `num)` ` ` `{` ` ` `int` `sum = ` `0` `;` ` ` `while` `(num > ` `0` `) ` ` ` `{` ` ` `sum += (num % ` `10` `);` ` ` `num /= ` `10` `;` ` ` `}` ` ` `return` `sum;` ` ` `}` ` ` `// Function to perform dfs` ` ` `static` `void` `dfs(` `int` `node, ` `int` `parent)` ` ` `{` ` ` `// Check if the digit sum` ` ` `// of the node weight` ` ` `// is even or not` ` ` `if` `(!(digitSum(weight[node]) % ` `2` `== ` `1` `))` ` ` `ans = Math.max(ans, weight[node]);` ` ` `// Performing DFS to iterate the` ` ` `// remaining nodes` ` ` `for` `(` `int` `to : graph[node]) ` ` ` `{` ` ` `if` `(to == parent)` ` ` `continue` `;` ` ` `dfs(to, node);` ` ` `}` ` ` `}` ` ` `// Driver code` ` ` `public` `static` `void` `main(String[] args)` ` ` `{` ` ` `// Weights of the node` ` ` `weight[` `1` `] = ` `5` `;` ` ` `weight[` `2` `] = ` `10` `;` ` ` `weight[` `3` `] = ` `11` `;` ` ` `weight[` `4` `] = ` `8` `;` ` ` `weight[` `5` `] = ` `6` `;` ` ` `for` `(` `int` `i = ` `0` `; i < graph.length; i++)` ` ` `graph[i] = ` `new` `Vector<Integer>();` ` ` `// Edges of the tree` ` ` `graph[` `1` `].add(` `2` `);` ` ` `graph[` `2` `].add(` `3` `);` ` ` `graph[` `2` `].add(` `4` `);` ` ` `graph[` `1` `].add(` `5` `);` ` ` `// Call the dfs function to` ` ` `// traverse through the tree` ` ` `dfs(` `1` `, ` `1` `);` ` ` `System.out.print(ans + ` `"\n"` `);` ` ` `}` `}` `// This code contributed by Princi Singh` |

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## Python3

`# Python3 program to find the` `# maximum weighing node` `# in the tree whose weight` `# has an Even Digit Sum` `sz ` `=` `1e5` `ans ` `=` `-` `1` `graph ` `=` `[[] ` `for` `i ` `in` `range` `(` `100` `)]` `weight ` `=` `[` `-` `1` `] ` `*` `100` `# Function to find the digit sum` `# for a number` `def` `digitSum(num):` ` ` `sum` `=` `0` ` ` `while` `num:` ` ` `sum` `+` `=` `num ` `%` `10` ` ` `num ` `=` `num ` `/` `/` `10` ` ` `return` `sum` `# Function to perform dfs` `def` `dfs(node, parent):` ` ` `global` `ans` ` ` `# Check if the digit sum` ` ` `# of the node weight` ` ` `# is even or not` ` ` `if` `not` `(digitSum(weight[node]) & ` `1` `):` ` ` `ans ` `=` `max` `(ans, weight[node])` ` ` `# Performing DFS to iterate the` ` ` `# remaining nodes` ` ` `for` `to ` `in` `graph[node]:` ` ` `if` `to ` `=` `=` `parent:` ` ` `continue` ` ` `dfs(to, node)` `# Driver code` `def` `main():` ` ` `# 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` `)` ` ` `# Call the dfs function to` ` ` `# traverse through the tree` ` ` `dfs(` `1` `, ` `1` `)` ` ` `print` `(ans)` `main()` `# This code is contributed by stutipathak31jan` |

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## C#

`// C# program to find the` `// maximum weighing node` `// in the tree whose weight` `// has an Even Digit Sum` `using` `System;` `using` `System.Collections.Generic;` `class` `GFG ` `{` ` ` `static` `int` `sz = (` `int` `)1e5;` ` ` `static` `int` `ans = -1;` ` ` `static` `List<` `int` `>[] graph = ` `new` `List<` `int` `>[ 100 ];` ` ` `static` `int` `[] weight = ` `new` `int` `[100];` ` ` `// Function to find the digit sum` ` ` `// for a number` ` ` `static` `int` `digitSum(` `int` `num)` ` ` `{` ` ` `int` `sum = 0;` ` ` `while` `(num > 0) ` ` ` `{` ` ` `sum += (num % 10);` ` ` `num /= 10;` ` ` `}` ` ` `return` `sum;` ` ` `}` ` ` `// Function to perform dfs` ` ` `static` `void` `dfs(` `int` `node, ` `int` `parent)` ` ` `{` ` ` `// Check if the digit sum` ` ` `// of the node weight` ` ` `// is even or not` ` ` `if` `(!(digitSum(weight[node]) % 2 == 1))` ` ` `ans = Math.Max(ans, weight[node]);` ` ` `// Performing DFS to iterate the` ` ` `// remaining nodes` ` ` `foreach` `(` `int` `to ` `in` `graph[node])` ` ` `{` ` ` `if` `(to == parent)` ` ` `continue` `;` ` ` `dfs(to, node);` ` ` `}` ` ` `}` ` ` `// Driver code` ` ` `public` `static` `void` `Main(String[] args)` ` ` `{` ` ` `// Weights of the node` ` ` `weight[1] = 5;` ` ` `weight[2] = 10;` ` ` `weight[3] = 11;` ` ` `weight[4] = 8;` ` ` `weight[5] = 6;` ` ` `for` `(` `int` `i = 0; i < graph.Length; i++)` ` ` `graph[i] = ` `new` `List<` `int` `>();` ` ` `// Edges of the tree` ` ` `graph[1].Add(2);` ` ` `graph[2].Add(3);` ` ` `graph[2].Add(4);` ` ` `graph[1].Add(5);` ` ` `// Call the dfs function to` ` ` `// traverse through the tree` ` ` `dfs(1, 1);` ` ` `Console.Write(ans + ` `"\n"` `);` ` ` `}` `}` `// This code is contributed by Rajput-Ji` |

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**Output**

11

__Complexity Analysis:__

**Time Complexity :** O(N).

In dfs, every node of the tree is processed once and hence the complexity due to the dfs is O(N) if there are total N nodes in the tree. Also, for processing each node the DigitSum() function is used which has a complexity of O(d), where d is the number of digits in the weight of a node, however since the weight of any node is an integer so it can only have 10 digits at max hence this function does not affect the overall time complexity. Therefore, the time complexity is O(N).

**Auxiliary Space :** O(1).

Any extra space is not required, so the space complexity is constant.