even_tree.cpp

#include <bits/stdc++.h>

using namespace std;

string ltrim(const string &);
string rtrim(const string &);
vector<string> split(const string &);

int DFS_helper(list<int> *l,vector<bool> &visited,int *ans,int node)
{
    int temp=0,num=0;
    visited[node]=true;
    for(auto a : l[node])
    {
        if(visited[a]==false)
        {
            temp=DFS_helper(l,visited,ans,a);
            (temp%2)? num+=temp : ((*ans)++); 
        }
            
    }
    
    return num+1;
}


 int DFS(list<int> *l)
 {
     int ans=0;
     vector<bool> visited(l->size());    
     DFS_helper(l,visited,&ans,1);
     return ans;
 
 }


int evenForest(int t_nodes, int t_edges, vector<int> t_from, vector<int> t_to) {
    
    list<int> *l = new list<int>[t_nodes+1];
    
    for(int i=0;i<t_from.size();i++)   //making adjacency list out of the array
    {
        l[t_from[i]].push_back(t_to[i]);
        l[t_to[i]].push_back(t_from[i]);
    }
     
     return DFS(l);
}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string t_nodes_edges_temp;
    getline(cin, t_nodes_edges_temp);

    vector<string> t_nodes_edges = split(rtrim(t_nodes_edges_temp));

    int t_nodes = stoi(t_nodes_edges[0]);
    int t_edges = stoi(t_nodes_edges[1]);

    vector<int> t_from(t_edges);
    vector<int> t_to(t_edges);

    for (int i = 0; i < t_edges; i++) {
        string t_from_to_temp;
        getline(cin, t_from_to_temp);

        vector<string> t_from_to = split(rtrim(t_from_to_temp));

        int t_from_temp = stoi(t_from_to[0]);
        int t_to_temp = stoi(t_from_to[1]);

        t_from[i] = t_from_temp;
        t_to[i] = t_to_temp;
    }

    int res = evenForest(t_nodes, t_edges, t_from, t_to);

    fout << res << "\n";

    fout.close();

    return 0;
}

string ltrim(const string &str) {
    string s(str);

    s.erase(
        s.begin(),
        find_if(s.begin(), s.end(), not1(ptr_fun<int, int>(isspace)))
    );

    return s;
}

string rtrim(const string &str) {
    string s(str);

    s.erase(
        find_if(s.rbegin(), s.rend(), not1(ptr_fun<int, int>(isspace))).base(),
        s.end()
    );

    return s;
}

vector<string> split(const string &str) {
    vector<string> tokens;

    string::size_type start = 0;
    string::size_type end = 0;

    while ((end = str.find(" ", start)) != string::npos) {
        tokens.push_back(str.substr(start, end - start));

        start = end + 1;
    }

    tokens.push_back(str.substr(start));

    return tokens;
}