luogu

链接:https://www.luogu.org/problem/P5180
思路:有向图支配树裸题,纯粹放一个板子在这里。。。。。具体内容看上一篇,待补。

代码:

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using namespace std;

typedef long long ll;
typedef double db;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vp;
const int inf = 1e9;
const ll INF = 1e18;

#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define mem(a) memset(a, 0, sizeof(a))
#define PA puts("pass")
#define lowbit(x) (x & -x)
const int maxn = 2e5 + 5;
vi g[maxn], rg[maxn], ng[maxn], G[maxn];
int n, m;
int dfn[maxn], id[maxn], dfs_clock, fa[maxn], f[maxn];
int semi[maxn], idom[maxn], mn[maxn], ans[maxn];

int (int x){
if(x == f[x]) return x;
int p = find(f[x]);
if(dfn[semi[mn[f[x]]]] < dfn[semi[mn[x]]]) mn[x] = mn[f[x]];
return f[x] = p;
}

void dfs(int u){
dfn[u] = ++dfs_clock, id[dfs_clock] = u;
for(auto &v : g[u]){
if(dfn[v]) continue;
fa[v] = u;
dfs(v);
}
}


void tarjan(){
for(int i = dfs_clock; i > 1; i--){
int u = id[i];
for(auto &v : rg[u]){
if(!dfn[v]) continue;
find(v);
if(dfn[semi[mn[v]]] < dfn[semi[u]]) semi[u] = semi[mn[v]];
}
ng[semi[u]].eb(u);
f[u] = fa[u];
u = fa[u];
for(auto &v : ng[u]){
find(v);
if(semi[mn[v]] == u) idom[v] = u;
else idom[v] = mn[v];
}
}
for(int i = 2; i <= dfs_clock; i++){
int u = id[i];
if(idom[u] != semi[u]) idom[u] = idom[idom[u]];
}
}

void getans(int u){
ans[u] = 1;
for(auto &v : G[u]){
getans(v);
ans[u] += ans[v];
}
}


int main(){
ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
cin >> n >> m;
for (int i = 1; i <= n; ++i) {
semi[i] = mn[i] = f[i] = i;
}
for (int i = 1; i <= m; ++i) {
int u, v;
cin >> u >> v;
g[u].eb(v);
rg[v].eb(u);
}
dfs(1);
tarjan();
for(int i = 2; i <= n; i++) G[idom[i]].eb(i); //除了起点外都要建图
getans(1); //起点结束
for(int i = 1; i <= n; i++) cout << ans[i] << (i == n ? 'n' : ' ');
return 0;
}