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dsu.cpp
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dsu.cpp
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#include <vector>
#include <iostream>
#include <cstdlib>
using namespace std;
struct dsu {
vector<int> cha, rank, n, m;
dsu(int N): cha(N+1), n(N+1), m(N+1) {
for (int i=1; i<=N; i++) {
cha[i] = i;
m[i] = 0;
n[i] = 1;
}
}
int find(int u) {
if (cha[u] != u) cha[u] = find(cha[u]);
return cha[u];
}
void join(int u, int v) {
u = find(u), v = find(v);
if (u == v) {
m[u]++;
return;
}
if (rand()&1) swap(u, v);
cha[v] = u;
n[u] += n[v];
m[u] += m[v] + 1;
}
};
int main() {
ios::sync_with_stdio(false); cin.tie(0);
int n, m; cin >> n >> m;
dsu d(n);
while (m--) {
int u, v; cin >> u >> v;
d.join(u, v);
}
int res = 0;
for (int i=1; i<=n; i++) if (d.cha[i] == i) res += d.m[i] - d.n[i] + 1;
cout << res;
return 0;
}