Sum of nodes on the longest path from root to leaf node

• Difficulty Level : Medium
• Last Updated : 27 Sep, 2021

Given a binary tree containing n nodes. The problem is to find the sum of all nodes on the longest path from root to leaf node. If two or more paths compete for the longest path, then the path having maximum sum of nodes is being considered.
Examples:

Input : Binary tree:
4
/ \
2   5
/ \ / \
7  1 2  3
/
6
Output : 13

4
/ \
2   5
/ \ / \
7  1 2  3
/
6

The highlighted nodes (4, 2, 1, 6) above are
part of the longest root to leaf path having
sum = (4 + 2 + 1 + 6) = 13

Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

Approach: Recursively find the length and sum of nodes of each root to leaf path and accordingly update the maximum sum.
Algorithm:

sumOfLongRootToLeafPath(root, sum, len, maxLen, maxSum)
if root == NULL
if maxLen < len
maxLen = len
maxSum = sum
else if maxLen == len && maxSum is less than sum
maxSum = sum
return

sumOfLongRootToLeafPath(root-left, sum + root-data,
len + 1, maxLen, maxSum)
sumOfLongRootToLeafPath(root-right, sum + root-data,
len + 1, maxLen, maxSum)

sumOfLongRootToLeafPathUtil(root)
if (root == NULL)
return 0

Declare maxSum = Minimum Integer
Declare maxLen = 0
sumOfLongRootToLeafPath(root, 0, 0, maxLen, maxSum)
return maxSum

C++

 // C++ implementation to find the sum of nodes// on the longest path from root to leaf node#include  using namespace std; // Node of a binary treestruct Node {    int data;    Node* left, *right;}; // function to get a new nodeNode* getNode(int data){    // allocate memory for the node    Node* newNode = (Node*)malloc(sizeof(Node));     // put in the data    newNode->data = data;    newNode->left = newNode->right = NULL;    return newNode;} // function to find the sum of nodes on the// longest path from root to leaf nodevoid sumOfLongRootToLeafPath(Node* root, int sum,                      int len, int& maxLen, int& maxSum){    // if true, then we have traversed a    // root to leaf path    if (!root) {        // update maximum length and maximum sum        // according to the given conditions        if (maxLen < len) {            maxLen = len;            maxSum = sum;        } else if (maxLen == len && maxSum < sum)            maxSum = sum;        return;    }     // recur for left subtree    sumOfLongRootToLeafPath(root->left, sum + root->data,                            len + 1, maxLen, maxSum);     // recur for right subtree    sumOfLongRootToLeafPath(root->right, sum + root->data,                            len + 1, maxLen, maxSum);} // utility function to find the sum of nodes on// the longest path from root to leaf nodeint sumOfLongRootToLeafPathUtil(Node* root){    // if tree is NULL, then sum is 0    if (!root)        return 0;     int maxSum = INT_MIN, maxLen = 0;     // finding the maximum sum 'maxSum' for the    // maximum length root to leaf path    sumOfLongRootToLeafPath(root, 0, 0, maxLen, maxSum);     // required maximum sum    return maxSum;} // Driver program to test aboveint main(){    // binary tree formation    Node* root = getNode(4);         /*        4        */    root->left = getNode(2);         /*       / \       */    root->right = getNode(5);        /*      2   5      */    root->left->left = getNode(7);   /*     / \ / \     */    root->left->right = getNode(1);  /*    7  1 2  3    */    root->right->left = getNode(2);  /*      /          */    root->right->right = getNode(3); /*     6           */    root->left->right->left = getNode(6);     cout << "Sum = "         << sumOfLongRootToLeafPathUtil(root);     return 0;}

Java

 // Java implementation to find the sum of nodes// on the longest path from root to leaf nodepublic class GFG{                           // Node of a binary tree    static class Node {        int data;        Node left, right;                 Node(int data){            this.data = data;            left = null;            right = null;        }    }    static int maxLen;    static int maxSum;         // function to find the sum of nodes on the    // longest path from root to leaf node    static void sumOfLongRootToLeafPath(Node root, int sum,                                         int len)    {        // if true, then we have traversed a        // root to leaf path        if (root == null) {            // update maximum length and maximum sum            // according to the given conditions            if (maxLen < len) {                maxLen = len;                maxSum = sum;            } else if (maxLen == len && maxSum < sum)                maxSum = sum;            return;        }                          // recur for left subtree        sumOfLongRootToLeafPath(root.left, sum + root.data,                                len + 1);                 sumOfLongRootToLeafPath(root.right, sum + root.data,                                len + 1);             }          // utility function to find the sum of nodes on    // the longest path from root to leaf node    static int sumOfLongRootToLeafPathUtil(Node root)    {        // if tree is NULL, then sum is 0        if (root == null)            return 0;              maxSum = Integer.MIN_VALUE;        maxLen = 0;              // finding the maximum sum 'maxSum' for the        // maximum length root to leaf path        sumOfLongRootToLeafPath(root, 0, 0);              // required maximum sum        return maxSum;    }          // Driver program to test above    public static void main(String args[])    {        // binary tree formation        Node root = new Node(4);         /*        4        */        root.left = new Node(2);         /*       / \       */        root.right = new Node(5);        /*      2   5      */        root.left.left = new Node(7);    /*     / \ / \     */        root.left.right = new Node(1);   /*    7  1 2  3    */        root.right.left = new Node(2);   /*      /          */        root.right.right = new Node(3);  /*     6           */        root.left.right.left = new Node(6);              System.out.println( "Sum = "             + sumOfLongRootToLeafPathUtil(root));    }}// This code is contributed by Sumit Ghosh

Python3

 # Python3 implementation to find the # Sum of nodes on the longest path# from root to leaf nodes # function to get a new nodeclass getNode:    def __init__(self, data):         # put in the data        self.data = data        self.left = self.right = None # function to find the Sum of nodes on the# longest path from root to leaf nodedef SumOfLongRootToLeafPath(root, Sum, Len,                            maxLen, maxSum):                                     # if true, then we have traversed a    # root to leaf path    if (not root):                 # update maximum Length and maximum Sum        # according to the given conditions        if (maxLen < Len):            maxLen = Len            maxSum = Sum        elif (maxLen== Len and              maxSum < Sum):            maxSum = Sum        return     # recur for left subtree    SumOfLongRootToLeafPath(root.left, Sum + root.data,                            Len + 1, maxLen, maxSum)     # recur for right subtree    SumOfLongRootToLeafPath(root.right, Sum + root.data,                            Len + 1, maxLen, maxSum) # utility function to find the Sum of nodes on# the longest path from root to leaf nodedef SumOfLongRootToLeafPathUtil(root):         # if tree is NULL, then Sum is 0    if (not root):        return 0     maxSum = [-999999999999]    maxLen =      # finding the maximum Sum 'maxSum' for    # the maximum Length root to leaf path    SumOfLongRootToLeafPath(root, 0, 0,                            maxLen, maxSum)     # required maximum Sum    return maxSum # Driver Codeif __name__ == '__main__':         # binary tree formation    root = getNode(4)         #     4        root.left = getNode(2)         #     / \        root.right = getNode(5)     #     2 5        root.left.left = getNode(7) #     / \ / \        root.left.right = getNode(1) # 7 1 2 3    root.right.left = getNode(2) #     /            root.right.right = getNode(3) #     6            root.left.right.left = getNode(6)     print("Sum = ", SumOfLongRootToLeafPathUtil(root))     # This code is contributed by PranchalK

C#

 using System; // c# implementation to find the sum of nodes// on the longest path from root to leaf nodepublic class GFG{    // Node of a binary tree    public class Node    {        public int data;        public Node left, right;         public Node(int data)        {            this.data = data;            left = null;            right = null;        }    }    public static int maxLen;    public static int maxSum;     // function to find the sum of nodes on the    // longest path from root to leaf node    public static void sumOfLongRootToLeafPath(Node root, int sum, int len)    {        // if true, then we have traversed a        // root to leaf path        if (root == null)        {            // update maximum length and maximum sum            // according to the given conditions            if (maxLen < len)            {                maxLen = len;                maxSum = sum;            }            else if (maxLen == len && maxSum < sum)            {                maxSum = sum;            }            return;        }          // recur for left subtree        sumOfLongRootToLeafPath(root.left, sum + root.data, len + 1);         sumOfLongRootToLeafPath(root.right, sum + root.data, len + 1);     }     // utility function to find the sum of nodes on    // the longest path from root to leaf node    public static int sumOfLongRootToLeafPathUtil(Node root)    {        // if tree is NULL, then sum is 0        if (root == null)        {            return 0;        }         maxSum = int.MinValue;        maxLen = 0;         // finding the maximum sum 'maxSum' for the        // maximum length root to leaf path        sumOfLongRootToLeafPath(root, 0, 0);         // required maximum sum        return maxSum;    }     // Driver program to test above    public static void Main(string[] args)    {        // binary tree formation        Node root = new Node(4); //        4        root.left = new Node(2); //       / \        root.right = new Node(5); //      2   5        root.left.left = new Node(7); //     / \ / \        root.left.right = new Node(1); //    7  1 2  3        root.right.left = new Node(2); //      /        root.right.right = new Node(3); //     6        root.left.right.left = new Node(6);         Console.WriteLine("Sum = " + sumOfLongRootToLeafPathUtil(root));    }}   // This code is contributed by Shrikant13

Javascript


Output
Sum = 13

Time Complexity: O(n)

Another Approach: Using level order traversal

1. Create a structure containing the current Node, level and sum in the path.
2. Push the root element with level 0 and sum as the root’s data.
3. Pop the front element and update the maximum level sum and maximum level if needed.
4. Push the left and right nodes if exists.
5. Do the same for all the nodes in tree.

C++

 #include using namespace std; //Building a tree node having left and right pointers set to null initiallystruct Node{  Node* left;  Node* right;  int data;  //constructor to set the data of the newly created tree node  Node(int element){     data = element;     this->left = nullptr;     this->right = nullptr;  }}; int longestPathLeaf(Node* root){     /* structure to store current Node,it's level and sum in the path*/  struct Element{    Node* data;    int level;    int sum;  };     /*    maxSumLevel stores maximum sum so far in the path    maxLevel stores maximum level so far  */  int maxSumLevel = root->data,maxLevel = 0;   /* queue to implement level order traversal */     list que;  Element e;     /* Each element variable stores the current Node, it's level, sum in the path */   e.data = root;  e.level = 0;  e.sum = root->data;     /* push the root element*/  que.push_back(e);     /* do level order traversal on the tree*/  while(!que.empty()){      Element front = que.front();     Node* curr = front.data;     que.pop_front();           /* if the level of current front element is greater than the maxLevel so far then update maxSum*/     if(front.level > maxLevel){        maxSumLevel = front.sum;        maxLevel = front.level;     }     /* if another path competes then update if the sum is greater than the previous path of same height*/     else if(front.level == maxLevel && front.sum > maxSumLevel)        maxSumLevel = front.sum;      /* push the left element if exists*/      if(curr->left){        e.data = curr->left;        e.sum = e.data->data;        e.sum +=  front.sum;        e.level = front.level+1;        que.push_back(e);     }     /*push the right element if exists*/     if(curr->right){        e.data = curr->right;        e.sum = e.data->data;        e.sum +=  front.sum;        e.level = front.level+1;        que.push_back(e);     }  }   /*return the answer*/  return maxSumLevel;}//Helper functionint main() {     Node* root = new Node(4);          root->left = new Node(2);          root->right = new Node(5);         root->left->left = new Node(7);    root->left->right = new Node(1);   root->right->left = new Node(2);  root->right->right = new Node(3);  root->left->right->left = new Node(6);     cout << longestPathLeaf(root) << "\n";       return 0;}
Output
13

Time Complexity: O(N)
Auxiliary Space: O(N)

Contributed by Manjukrishna

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