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Maximum Level Sum of a Binary Tree in C++
Suppose we have the root of a binary tree, the level of its root is 1, the level of its children is 2, and so on. We have to return the smallest level X such that the sum of all the values of nodes at level X is maximal. So if the tree is like −
Then the output will be 2, The level 1 sum = 1, level 2 sum is 7 + 0 = 7, level 2 sum is 7 + (-8) = -1, so max is of level 2, so output is 2.
To solve this, we will follow these steps −
- level := 1, sum := value of r, ansLevel := level, ansSum := sum
- define a queue q, insert given node r into q
- while q is not empty
- capacity := size of q
- increase level by 1, sum := 0
- while capacity is not 0
- node := front node from q, delete node from q
- if right of node is valid, then sum := sum + value of right node, insert right node into q
- if left of node is valid, then sum := sum + value of left node, insert left node into q
- decrease capacity by 1
- if ansSum < sum, then ansSum := sum, ansLevel := level
- return ansLevel
Example(C++)
Let us see the following implementation to get a better understanding −
Live Demo 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 maxLevelSum(TreeNode* r) {
int level = 1, sum = r->val;
int ansLevel = level, ansSum = sum;
queue <TreeNode*> q;
q.push(r);
while(!q.empty()){
int capacity = q.size();
level++;
sum = 0;
while(capacity--){
TreeNode* node = q.front();
q.pop();
if(node->right){
sum += node->right->val;
q.push(node->right);
}
if(node->left){
sum += node->left->val;
q.push(node->left);
}
}
if(ansSum<sum){
ansSum = sum;
ansLevel = level;
}
}
return ansLevel;
}
};
main(){
vector<int> v = {1,7,0,7,-8,NULL,NULL};
TreeNode *root = make_tree(v);
Solution ob;
cout <<ob.maxLevelSum(root);
}Input
[1,7,0,7,-8,null,null]
Output
2
Updated on: 30-Apr-2020
178 Views
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