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

C++Server Side ProgrammingProgramming

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

Let us see the following implementation to get better understanding −

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;
   }
};

Input

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

Output

18
raja
Published on 18-Mar-2020 05:47:46
Advertisements