Find most frequent value of ancestors for each Node of given Tree

#include <bits/stdc++.h>

using namespace std;

unordered_map<int, int> ans;

unordered_map<int, int> freq;

set<pair<int, int> > s;

void addEdge(vector<int> adj[], int u, int v)

{

    adj[u].push_back(v);

    adj[v].push_back(u);

}

void helper(int v, int flag)

{

    if (s.find({ freq[v], v }) != s.end())

        s.erase(s.find({ freq[v], v }));

    freq[v] += flag;

    s.insert({ freq[v], v });

}

void ModeOfAncestors(vector<int> adj[], int node,

                     vector<int>& vis, vector<int>& val)

{

    int v = val[node];

    helper(v, 1);

    ans[node] = (*(--s.end())).second;

    vis[node] = 1;

    for (auto child : adj[node]) {

        if (vis[child] == 0)

            ModeOfAncestors(adj, child, vis, val);

    }

    helper(v, -1);

}

int main()

{

    int N = 9;

    vector<int> adj[N];

    addEdge(adj, 0, 1);

    addEdge(adj, 0, 2);

    addEdge(adj, 1, 3);

    addEdge(adj, 1, 4);

    addEdge(adj, 1, 5);

    addEdge(adj, 2, 6);

    addEdge(adj, 2, 7);

    addEdge(adj, 2, 8);

    vector<int> val = { 5, 2, 3, 2, 5, 1, 3, 5, 1 };

    vector<int> vis(N, 0);

    ModeOfAncestors(adj, 0, vis, val);

    for (int i = 0; i < N; i++)

        cout << ans[i] << " ";

    cout << endl;

    return 0;

}

#include <bits/stdc++.h>

using namespace std;

unordered_map<int, int> ans;

unordered_map<int, int> freq;

set<pair<int, int> > s;

void addEdge(vector<int> adj[], int u, int v)

{

    adj[u].push_back(v);

    adj[v].push_back(u);

}

void helper(int v, int flag)

{

    if (s.find({ freq[v], v }) != s.end())

        s.erase(s.find({ freq[v], v }));

    freq[v] += flag;

    s.insert({ freq[v], v });

}

void ModeOfAncestors(vector<int> adj[], int node,

                     vector<int>& vis, vector<int>& val)

{

    int v = val[node];

    helper(v, 1);

    ans[node] = (*(--s.end())).second;

    vis[node] = 1;

    for (auto child : adj[node]) {

        if (vis[child] == 0)

            ModeOfAncestors(adj, child, vis, val);

    }

    helper(v, -1);

}

int main()

{

    int N = 9;

    vector<int> adj[N];

    addEdge(adj, 0, 1);

    addEdge(adj, 0, 2);

    addEdge(adj, 1, 3);

    addEdge(adj, 1, 4);

    addEdge(adj, 1, 5);

    addEdge(adj, 2, 6);

    addEdge(adj, 2, 7);

    addEdge(adj, 2, 8);

    vector<int> val = { 5, 2, 3, 2, 5, 1, 3, 5, 1 };

    vector<int> vis(N, 0);

    ModeOfAncestors(adj, 0, vis, val);

    for (int i = 0; i < N; i++)

        cout << ans[i] << " ";

    cout << endl;

    return 0;

}