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