TheAlgorithms-C-Plus-Plus/dynamic_programming/tree_height.cpp

/// C++ Program to find height of the tree using bottom0-up DP.

/**
 * Given a rooted tree with node 1.
 * Task is to find the height of the tree.
**/

#include<iostream>
#include<vector>


/// global declarations

/// no of nodes max limit.
const int MAX = 1e5;

/// adjacency list
std::vector<int> adj[MAX];

std::vector<bool> visited;
std::vector<int> dp;

void dp_with_dfs(int u) {
    visited[u] = true;
    int child_height = 1;
    for (int v : adj[u]) {
        if (!visited[v]) {
            dp_with_dfs(v);

            /// selected maximum subtree height from all childs.
            child_height = std::max(child_height, dp[v]+1);
        }
    }

    /// assigned the max child height to current visited node.
    dp[u] = child_height;
}

int main(){

    /// number of nodes
    int n;
    std::cin >> n;

    int u,v;

    /// a valid tree contains exactly n-1 edges where n denotes the nodes.
    for (int i=0; i < n-1; i++) {
        std::cin >> u >> v;

        /// undirected tree u -> v and v -> u.
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    /// initialize all nodes as unvisited.
    visited.assign(n+1,false);

    /// initialize depth of all nodes to 0.
    dp.assign(n+1,0);

    /// call to dp_with_dfs which will initialize the height of all nodes in dp vector.
    dp_with_dfs (1);

    std::cout << dp[1] << std::endl;
}