Maximum Consecutive Increasing Path Length in Binary Tree in C++

Suppose we have a binary tree; we have to calculate the length of the longest path which consists of nodes with consecutive values in increasing order. Every node will be treated as a path of length 1.

So, if the input is like

then the output will be 3 as (11, 12, 13) is maximum consecutive path.

To solve this, we will follow these steps −

• Define a function solve(), this will take root, prev_data, prev_length,
• if not root is non-zero, then −
  • return prev_length
• cur_data := val of root
• if cur_data is same as prev_data + 1, then −
  • return maximum of solve(left of root, cur_data, prev_length+1) and solve(right of root, cur_data, prev_length+1)
• newPathLen := maximum of solve(left of root, cur_data, 1) and solve(right of root, cur_data, 1)
• return maximum of prev_length and newPathLen
• From the main method do the following −
• if root is same as NULL, then −
  • return 0
• return solve(root, val of root-1, 0)

Example (C++)

Let us see the following implementation to get 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;       } }; int solve(TreeNode *root, int prev_data, int prev_length){    if (!root)       return prev_length;    int cur_data = root->val;    if (cur_data == prev_data+1){       return max(solve(root->left, cur_data, prev_length+1), solve(root->right, cur_data, prev_length+1));    }    int newPathLen = max(solve(root->left, cur_data, 1), solve(root->right, cur_data, 1));    return max(prev_length, newPathLen); } int maxLen(TreeNode *root){    if (root == NULL)       return 0;    return solve(root, root->val-1, 0); } int main(){    TreeNode *root = new TreeNode(10);    root->left = new TreeNode(11);    root->right = new TreeNode(9);    root->left->left = new TreeNode(13);    root->left->right = new TreeNode(12);    root->right->left = new TreeNode(13);    root->right->right = new TreeNode(8);    cout << maxLen(root);    return 0; }

Input

TreeNode *root = new TreeNode(10); root->left = new TreeNode(11); root->right = new TreeNode(9); root->left->left = new TreeNode(13); root->left->right = new TreeNode(12); root->right->left = new TreeNode(13); root->right->right = new TreeNode(8);

Output

3