Longest consecutive sequence in Binary tree
Last Updated :
10 Mar, 2023
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Given a Binary Tree find the length of the longest path which comprises of nodes with consecutive values in increasing order. Every node is considered as a path of length 1.
Examples:
In below diagram binary tree with longest consecutive path(LCP) are shown :
We can solve above problem recursively. At each node we need information of its parent node, if current node has value one more than its parent node then it makes a consecutive path, at each node we will compare node’s value with its parent value and update the longest consecutive path accordingly.
For getting the value of parent node, we will pass the (node_value + 1) as an argument to the recursive method and compare the node value with this argument value, if satisfies, update the current length of consecutive path otherwise reinitialize current path length by 1.
Please see below code for better understanding :
Try it on GfG Practice 
// C/C++ program to find longest consecutive
// sequence in binary tree
#include <bits/stdc++.h>
using namespace std;
/* A binary tree node has data, pointer to left
child and a pointer to right child */
struct Node
{
int data;
Node *left, *right;
};
// A utility function to create a node
Node* newNode(int data)
{
Node* temp = new Node;
temp->data = data;
temp->left = temp->right = NULL;
return temp;
}
// Utility method to return length of longest
// consecutive sequence of tree
void longestConsecutiveUtil(Node* root, int curLength,
int expected, int& res)
{
if (root == NULL)
return;
// if root data has one more than its parent
// then increase current length
if (root->data == expected)
curLength++;
else
curLength = 1;
// update the maximum by current length
res = max(res, curLength);
// recursively call left and right subtree with
// expected value 1 more than root data
longestConsecutiveUtil(root->left, curLength,
root->data + 1, res);
longestConsecutiveUtil(root->right, curLength,
root->data + 1, res);
}
// method returns length of longest consecutive
// sequence rooted at node root
int longestConsecutive(Node* root)
{
if (root == NULL)
return 0;
int res = 0;
// call utility method with current length 0
longestConsecutiveUtil(root, 0, root->data, res);
return res;
}
// Driver code to test above methods
int main()
{
Node* root = newNode(6);
root->right = newNode(9);
root->right->left = newNode(7);
root->right->right = newNode(10);
root->right->right->right = newNode(11);
printf("%d\n", longestConsecutive(root));
return 0;
}
75
1
// C/C++ program to find longest consecutive2
// sequence in binary tree3
4
using namespace std;5
6
/* A binary tree node has data, pointer to left7
child and a pointer to right child */8
struct Node9
{10
int data;11
Node *left, *right;12
};13
14
// A utility function to create a node15
Node* newNode(int data)16
{17
Node* temp = new Node;18
temp->data = data;19
temp->left = temp->right = NULL;20
return temp;21
}22
23
// Utility method to return length of longest24
// consecutive sequence of tree25
void longestConsecutiveUtil(Node* root, int curLength,26
int expected, int& res)27
{28
if (root == NULL)29
return;30
31
// if root data has one more than its parent32
// then increase current length33
if (root->data == expected)34
curLength++;35
else36
curLength = 1;37
38
// update the maximum by current length39
res = max(res, curLength);40
41
// recursively call left and right subtree with42
// expected value 1 more than root data43
longestConsecutiveUtil(root->left, curLength,44
root->data + 1, res);45
longestConsecutiveUtil(root->right, curLength,46
root->data + 1, res);47
}48
49
// method returns length of longest consecutive50
// sequence rooted at node root51
int longestConsecutive(Node* root)52
{53
if (root == NULL)54
return 0;55
56
int res = 0;57
58
// call utility method with current length 059
longestConsecutiveUtil(root, 0, root->data, res);60
61
return res;62
}63
64
// Driver code to test above methods65
int main()66
{67
Node* root = newNode(6);68
root->right = newNode(9);69
root->right->left = newNode(7);70
root->right->right = newNode(10);71
root->right->right->right = newNode(11);72
73
printf("%d\n", longestConsecutive(root));74
return 0;75
}// Java program to find longest consecutive
// sequence in binary tree
class Node
{
int data;
Node left, right;
Node(int item)
{
data = item;
left = right = null;
}
}
class Result
{
int res = 0;
}
class BinaryTree
{
Node root;
// method returns length of longest consecutive
// sequence rooted at node root
int longestConsecutive(Node root)
{
if (root == null)
return 0;
Result res = new Result();
// call utility method with current length 0
longestConsecutiveUtil(root, 0, root.data, res);
return res.res;
}
// Utility method to return length of longest
// consecutive sequence of tree
private void longestConsecutiveUtil(Node root, int curlength,
int expected, Result res)
{
if (root == null)
return;
// if root data has one more than its parent
// then increase current length
if (root.data == expected)
curlength++;
else
curlength = 1;
// update the maximum by current length
res.res = Math.max(res.res, curlength);
// recursively call left and right subtree with
// expected value 1 more than root data
longestConsecutiveUtil(root.left, curlength, root.data + 1, res);
longestConsecutiveUtil(root.right, curlength, root.data + 1, res);
}
// Driver code
public static void main(String args[])
{
BinaryTree tree = new BinaryTree();
tree.root = new Node(6);
tree.root.right = new Node(9);
tree.root.right.left = new Node(7);
tree.root.right.right = new Node(10);
tree.root.right.right.right = new Node(11);
System.out.println(tree.longestConsecutive(tree.root));
}
}
// This code is contributed by shubham96301
# Python3 program to find longest consecutive
# sequence in binary tree
# A utility class to create a node
class newNode:
def __init__(self, data):
self.data = data
self.left = self.right = None
# Utility method to return length of
# longest consecutive sequence of tree
def longestConsecutiveUtil(root, curLength,
expected, res):
if (root == None):
return
# if root data has one more than its
# parent then increase current length
if (root.data == expected):
curLength += 1
else:
curLength = 1
# update the maximum by current length
res[0] = max(res[0], curLength)
# recursively call left and right subtree
# with expected value 1 more than root data
longestConsecutiveUtil(root.left, curLength,
root.data + 1, res)
longestConsecutiveUtil(root.right, curLength,
root.data + 1, res)
# method returns length of longest consecutive
# sequence rooted at node root
def longestConsecutive(root):
if (root == None):
return 0
res = [0]
# call utility method with current length 0
longestConsecutiveUtil(root, 0, root.data, res)
return res[0]
# Driver Code
if __name__ == '__main__':
root = newNode(6)
root.right = newNode(9)
root.right.left = newNode(7)
root.right.right = newNode(10)
root.right.right.right = newNode(11)
print(longestConsecutive(root))
# This code is contributed by PranchalK
// C# program to find longest consecutive
// sequence in binary tree
using System;
class Node
{
public int data;
public Node left, right;
public Node(int item)
{
data = item;
left = right = null;
}
}
class Result
{
public int res = 0;
}
class GFG
{
Node root;
// method returns length of longest consecutive
// sequence rooted at node root
int longestConsecutive(Node root)
{
if (root == null)
return 0;
Result res = new Result();
// call utility method with current length 0
longestConsecutiveUtil(root, 0, root.data, res);
return res.res;
}
// Utility method to return length of longest
// consecutive sequence of tree
private void longestConsecutiveUtil(Node root, int curlength,
int expected, Result res)
{
if (root == null)
return;
// if root data has one more than its parent
// then increase current length
if (root.data == expected)
curlength++;
else
curlength = 1;
// update the maximum by current length
res.res = Math.Max(res.res, curlength);
// recursively call left and right subtree with
// expected value 1 more than root data
longestConsecutiveUtil(root.left, curlength,
root.data + 1, res);
longestConsecutiveUtil(root.right, curlength,
root.data + 1, res);
}
// Driver code
public static void Main(String []args)
{
GFG tree = new GFG();
tree.root = new Node(6);
tree.root.right = new Node(9);
tree.root.right.left = new Node(7);
tree.root.right.right = new Node(10);
tree.root.right.right.right = new Node(11);
Console.WriteLine(tree.longestConsecutive(tree.root));
}
}
// This code is contributed by 29AjayKumar
<script>
// JavaScript program to find longest consecutive
// sequence in binary tree
class Node
{
constructor(item)
{
this.data=item;
this.left = this.right = null;
}
}
let res = 0;
let root;
function longestConsecutive(root)
{
if (root == null)
return 0;
res=[0];
// call utility method with current length 0
longestConsecutiveUtil(root, 0, root.data, res);
return res[0];
}
// Utility method to return length of longest
// consecutive sequence of tree
function longestConsecutiveUtil(root,curlength, expected,res)
{
if (root == null)
return;
// if root data has one more than its parent
// then increase current length
if (root.data == expected)
curlength++;
else
curlength = 1;
// update the maximum by current length
res[0] = Math.max(res[0], curlength);
// recursively call left and right subtree with
// expected value 1 more than root data
longestConsecutiveUtil(root.left, curlength,
root.data + 1, res);
longestConsecutiveUtil(root.right, curlength,
root.data + 1, res);
}
// Driver code
root = new Node(6);
root.right = new Node(9);
root.right.left = new Node(7);
root.right.right = new Node(10);
root.right.right.right = new Node(11);
document.write(longestConsecutive(root));
// This code is contributed by rag2127
</script>
Output
3
Time Complexity: O(N) where N is the Number of nodes in a given binary tree.
Auxiliary Space: O(log(N))
Also discussed on below link:
Maximum Consecutive Increasing Path Length in Binary Tree
