题解

#include <iostream>
#include <vector>
#include <queue>
using namespace std;

int main() {
ios::sync_with_stdio(false);
cin.tie(0);

int n, m;
cin >> n >> m;

vector<int> deg(n + 1, 0);
vector<vector<int>> graph(n + 1);

for (int i = 0; i < m; i++) {
    int a, b;
    cin >> a >> b;
    deg[a]++;
    deg[b]++;
    graph[a].push_back(b);
    graph[b].push_back(a);
}

vector<bool> visited(n + 1, false);
int ans = 0;

for (int i = 1; i <= n; i++) {
    if (!visited[i]) {
        queue<int> q;
        q.push(i);
        visited[i] = true;
        vector<int> comp;
        comp.push_back(i);

        while (!q.empty()) {
            int u = q.front();
            q.pop();
            for (int v : graph[u]) {
                if (!visited[v]) {
                    visited[v] = true;
                    q.push(v);
                    comp.push_back(v);
                }
            }
        }

        int total_deg = 0;
        int odd_count = 0;
        for (int node : comp) {
            total_deg += deg[node];
            if (deg[node] % 2 == 1) {
                odd_count++;
            }
        }

        if (total_deg == 0) {
            continue;
        }

        if (odd_count == 0) {
            ans++;
        } else {
            ans += odd_count / 2;
        }
    }
}

cout << ans << endl;

return 0;

}