이 제출은 이전 버전의 oj.uz에서 채점하였습니다. 현재는 제출 당시와는 다른 서버에서 채점을 하기 때문에, 다시 제출하면 결과가 달라질 수도 있습니다.
#include <bits/stdc++.h>
#define ll long long
#define rep(i,m,n) for(int i=(m); i<=(n); i++)
#define reb(i,m,n) for(int i=(m); i>=(n); i--)
#define pii pair<int,int>
#define pll pair<ll,ll>
#define MP make_pair
#define fs first
#define se second
#define bit(msk, i) ((msk >> i) & 1)
#define iter(id, v) for(auto id : v)
#define pb push_back
#define SZ(v) (ll)v.size()
#define ALL(v) v.begin(),v.end()
using namespace std;
mt19937_64 rd(chrono :: steady_clock :: now ().time_since_epoch().count());
ll Rand (ll l, ll r) { return uniform_int_distribution<ll> (l, r) (rd); }
const int N = 1e5 + 7;
const int Mod = 1e9 + 7;
const int INF = 1e9;
const ll BASE = 137;
const int szBL = 320;
int n, m, Q;
vector<int> ke[N], ke2[N];
int high[N], pa[N];
int S[N], E[N];
pii qr[N];
void pdfs (int u, int p) {
high[u] = high[p] + 1;
pa[u] = p;
iter (&v, ke[u]) {
if (v != p) pdfs(v, u);
}
}
int num[N], low[N], del[N];
int time_dfs = 0;
bool ok = 1;
stack<int> st;
void dfs (int u) {
num[u] = low[u] = ++time_dfs;
st.push(u);
iter (&v, ke2[u]) {
if (del[v]) continue;
if (!num[v]) {
dfs(v);
low[u] = min(low[u], low[v]);
}
else low[u] = min(low[u], num[v]);
}
if (num[u] == low[u]) {
int v;
int num = 0;
do {
v = st.top();
st.pop();
num ++;
del[v] = 1;
}while (v != u);
if (num > 1) ok = 0;
}
}
void solution () {
time_dfs = 0;
ok = 1;
rep (i, 1, n) vector<int> ().swap(ke[i]), vector<int> ().swap(ke2[i]), E[i] = S[i] = num[i] = low[i] = del[i] = 0;
cin >> n;
rep (i, 1, n - 1) {
int u, v;
cin >> u>> v;
ke[u].pb(v);
ke[v].pb(u);
}
pdfs(1, 0);
cin >> m;
rep (i, 1, m) {
cin >> qr[i].fs >> qr[i].se;
S[qr[i].fs] = i;
E[qr[i].se] = i;
}
rep (i, 1, m) {
int u = qr[i].fs, v = qr[i].se;
while (u != v) {
if (high[u] > high[v]) swap(u, v);
if (E[v]) ke2[i].pb(E[v]);
if (S[v]) ke2[S[v]].pb(i);
v = pa[v];
}
if (E[v]) ke2[i].pb(E[v]);
if (S[v]) ke2[S[v]].pb(i);
}
rep (i, 1, m) if (!num[i]) dfs(i);
if (ok) cout <<"Yes\n";
else cout<<"No\n";
}
#define file(name) freopen(name".inp","r",stdin); \
freopen(name".out","w",stdout);
int main () {
// file("c");
ios_base :: sync_with_stdio(false); cin.tie(0); cout.tie(0);
int num_Test = 1;
cin >> num_Test;
while (num_Test--)
solution();
}
/*
no bug challenge +4
mình có muốn dùng mảng này không?
4 5
1 3
4 1
1 2
3 2
2 1
return->break
*/
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