Submission #876915

#	Time	Username	Problem	Language	Result	Execution time	Memory
876915		Ivkosqn	Jail (JOI22_jail)	C++14	0 / 100	20 ms	7156 KiB

jail

#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;
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 5
• Subtask 3: 0 / 16
• Subtask 4: 0 / 28
• Subtask 5: 0 / 12
• Subtask 6: 0 / 11
• Subtask 7: 0 / 23