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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 −
#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
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