Diameter of Tree (in the form of parent pointer)

/***

Given a tree in the form of parent pointers of every node (for root assume parent pointer to be null), write code to find the diameter of tree.

IDEA: Space complexity O(1), time complexity(nlogn)

// mark non-leaf nodes

for each node do

  mark its direct parent node

end

// get max length

for each node do

  if node is marked then //non-leaf

    skip

  else // leaf

    visit all parent nodes until root and count the length

    keep the max length

  end

end

***/

#include<iostream>

using namespace std;

class node {

public:

       node(int);

       int data;

       bool visit;

       node *parent;

};

node :: node(int val) {

       data = val;

       visit = true;

       parent = nullptr;

}

int diameter_tree(node **n, int size) {

       int height = 0;

       // mark node to find leaf

       for(int i = 0; i<size; i++) {

       //Note: edge condition of parent

              if (n[i]->parent != nullptr)

                     n[i]->parent->visit = false;     

       }

       for(int i = 0; i<size; i++) {

              if(n[i]->visit) {

                     node *ptr = n[i];

                     int h = 0;

                     while(ptr != nullptr) {   

                           h++;

                           ptr = ptr->parent;  

                     }

                     if(h > height) height = h;

              }

       }     

       return height;      

}

void main() {

       node *n[7];

       for (int i = 0; i<7; i++)

              n[i] = new node(i+1);

       n[0]->parent = n[4];

       n[1]->parent = n[4];

       n[2]->parent = n[5];

       n[3]->parent = n[5];

       n[4]->parent = n[6];

       n[5]->parent = n[6];

       cout<<diameter_tree(n, 7)<<endl;

}