Sum of Nodes with Even-Valued Grandparent in C++

Suppose we have a binary tree, we have to find the sum of values of nodes with even-valued grandparent. (A grandparent of a node is the parent of its parent, if it exists.). If there are no such nodes with an even-valued grandparent, then return 0. So if the tree is like −

The output will be 18. The red nodes are nodes with even-value grandparent, while the blue nodes are the even valued grandparents.

To solve this, we will follow these steps −

• Define a map called parent
• Define a method called solve(), this will take node and par
• if node is null, then return
• if par is not null and par is present in parent and parent[par] is not 0 and value of parent[par] is even, then
  • res := res + value of node
• parent[node] := par
• solve(left of node, node)
• solve(right of node, node)
• From the main method, set res := 0, call solve(root, Null), then return res

Example(C++)

Let us see the following implementation to get a better understanding −

 Live Demo

#include <bits/stdc++.h> using namespace std; class TreeNode{    public:       int val;       TreeNode *left, *right;       TreeNode(int data){          val = data;          left = NULL;          right = NULL;       } }; void insert(TreeNode **root, int val){    queue<TreeNode*> q;    q.push(*root);    while(q.size()){       TreeNode *temp = q.front();       q.pop();       if(!temp->left){          if(val != NULL)             temp->left = new TreeNode(val);          else             temp->left = new TreeNode(0);          return;       }       else{          q.push(temp->left);       }       if(!temp->right){          if(val != NULL)             temp->right = new TreeNode(val);          else             temp->right = new TreeNode(0);          return;       }       else{          q.push(temp->right);       }    } } TreeNode *make_tree(vector<int> v){    TreeNode *root = new TreeNode(v[0]);    for(int i = 1; i<v.size(); i++){       insert(&root, v[i]);    }    return root; } class Solution { public:    int res;    map <TreeNode*, TreeNode*> parent;    void solve(TreeNode* node, TreeNode* par = NULL){       if(!node)return;       if(par && parent.count(par) && parent[par] && parent[par]->val % 2 == 0){          res += node->val;       }       parent[node] = par;       solve(node->left, node);       solve(node->right, node);    }    int sumEvenGrandparent(TreeNode* root) {       res = 0;       parent.clear();       solve(root);       return res;    } }; main(){    vector<int> v = {6,7,8,2,7,1,3,9,NULL,1,4,NULL,NULL,NULL,5};    TreeNode *root = make_tree(v);    Solution ob;    cout << (ob.sumEvenGrandparent(root)); }

Input

[6,7,8,2,7,1,3,9,null,1,4,null,null,null,5]

Output

18