This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
#define endl '\n'
using namespace std;
const int maxn = 120010;
int n, m, s[maxn], f[maxn], used[maxn], bef[maxn];
vector<int> v[maxn], g[maxn], paths[510];
int usedp[maxn];
void find_path(int ver){
used[ver] = 1;
for(int nb : v[ver]){
if(used[nb])
continue;
bef[nb] = ver;
find_path(nb);
}
}
void read(){
cin >> n;
for(int i = 1;i <= n;i++){
v[i].clear();
g[i].clear();
}
for(int i = 1;i <= m;i++)
paths[i].clear();
for(int i = 1;i <= n - 1;i++){
int x, y;
cin >> x >> y;
v[x].push_back(y);
v[y].push_back(x);
}
cin >> m;
for(int i = 1;i <= m;i++){
cin >> s[i] >> f[i];
for(int k = 1;k <= n;k++)
used[k] = 0;
find_path(s[i]);
paths[i].push_back(f[i]);
int x = f[i];
while(x != s[i]){
x = bef[x];
paths[i].push_back(x);
}
sort(paths[i].begin(), paths[i].end());
}
}
bool cycle = 0;
void DFS(int ver){
used[ver] = 1;
for(int nb : g[ver]){
if(!used[nb])
DFS(nb);
else if(used[nb] == 1)
cycle = 1;
}
used[ver] = 2;
}
void dfs(int ver){
used[ver] = 1;
for(int nb : v[ver]){
if(used[nb])
continue;
dfs(nb);
}
}
void solve(){
read();
for(int i = 1;i <= m;i++){
for(int nb : paths[i])
usedp[nb] = 1;
for(int j = 1;j <= m;j++){
if(i == j)
continue;
for(int k = 1;k <= n;k++)
used[k] = 0;
used[s[j]] = 1;
dfs(s[i]);
if(!used[f[i]]){
g[j].push_back(i);
continue;
}
if(usedp[s[j]]){
g[j].push_back(i);
continue;
}
int ans = -1, l = 0, r = paths[j].size() - 1;
while(l <= r){
int mid = (l + r) / 2;
if(paths[j][mid] <= f[i])
l = mid + 1, ans = mid;
else
r = mid - 1;
}
if(ans != -1 && paths[j][ans] == f[i]){
g[j].push_back(i);
}
}
for(int nb : paths[i])
usedp[nb] = 0;
}
cycle = 0;
memset(used, 0, sizeof(used));
for(int i = 1;i <= n;i++){
if(!used[i]){
DFS(i);
}
}
if(cycle)
cout << "No\n";
else
cout << "Yes\n";
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int t;
cin >> t;
while(t--){
solve();
}
return 0;
}
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |
# | Verdict | Execution time | Memory | Grader output |
---|
Fetching results... |