1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
| #include <bits/stdc++.h>
#define MAX_N 100001
#define ll long long
#define pll pair<ll, ll>
#define vpll vector<pll>
#define vll vector<ll>
#define vvll vector<vll>
#define all(a) begin(a), end(a)
using namespace std;
ll n, e;
bool vis1[MAX_N], vis2[MAX_N], vis3[MAX_N];
ll rep[MAX_N];
vll st;
void dfs1(ll u, vvll& adj) {
vis1[u] = true;
for(auto& v : adj[u])
if(!vis1[v])
dfs1(v, adj);
st.push_back(u);
}
void dfs2(ll u, ll r, vvll& radj) {
vis2[u] = true;
rep[u] = r;
for(auto& v : radj[u])
if(!vis2[v])
dfs2(v, r, radj);
}
ll solve(vpll& edges) {
vvll adj(n + 1), radj(n + 1);
memset(vis1, 0, sizeof(vis1));
memset(vis2, 0, sizeof(vis2));
memset(vis3, 0, sizeof(vis3));
memset(rep, 0, sizeof(rep));
for(auto& [u, v] : edges) {
adj[u].push_back(v);
radj[v].push_back(u);
}
for(ll i = 1; i <= n; i++)
if(!vis1[i])
dfs1(i, adj);
while(!st.empty()) {
auto u = st.back(); st.pop_back();
if(!vis2[u])
dfs2(u,u,radj);
}
ll res = 0;
unordered_set<ll> usll;
for(auto& [u, v] : edges) {
if(rep[u] == rep[v]) continue;
usll.insert(rep[v]);
}
for(ll i = 1; i <= n; i++) {
if(vis3[rep[i]]) continue;
vis3[rep[i]] = true;
if(!usll.count(rep[i]))
res++;
}
return res;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
ll tc;
cin>>tc;
while(tc--) {
cin>>n>>e;
ll u, v;
vpll edges;
while(e--) {
cin>>u>>v;
edges.push_back({u,v});
}
cout<<solve(edges)<<'\n';
}
return 0;
}
|
