Deepest Leaves Sum in C++

Suppose we have a binary tree, we have to find the sum of values of its deepest leaves. So if the tree is like −

Then the output will be 15.

To solve this, we will follow these steps −

• Define a map m, and maxDepth
• Define a recursive method solve(), this will take node and level, initially level is 0
• if node is not present, then return
• maxDepth := max of level and maxDepth
• increase m[level] by value of node
• solve(left of node, level + 1)
• solve(right of node, level + 1)
• In the main method, setup maxDepth := 0, then solve(root, 0)
• return m[maxDepth]

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 maxDepth;
   map <int, int> m;
   void solve(TreeNode* node, int level = 0){
      if(!node)return;
      maxDepth = max(level, maxDepth);
      m[level] += node->val;
      solve(node->left, level + 1);
      solve(node->right, level + 1);
   }
   int deepestLeavesSum(TreeNode* root) {
      maxDepth = 0;
      m.clear();
      solve(root);
      //cout << maxDepth << endl;
      return m[maxDepth];
   }
};
main(){
   vector<int> v = {1,2,3,4,5,NULL,6,7,NULL,NULL,NULL,NULL,8};
   TreeNode *root = make_tree(v);
   Solution ob;
   cout << (ob.deepestLeavesSum(root));
}

Input

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

Output

15