Submission #1154924

#	Time	Username	Problem	Language	Result	Execution time	Memory
1154924		pemguimn	Through Another Maze Darkly (CCO21_day1problem3)	C++20	0 / 25	9094 ms	30144 KiB

Main

#include <bits/stdc++.h>
#define int long long
#define pii pair<int, int>

using namespace std;
const int N = 2e5 + 5, MOD = 1e9 + 7;  

int n, q;

vector<pii> adj[N];
int p[N], pt[N], eid[N], vid[N], ans[N], timedfs = 0, ee = 0, s = 0;
vector<int> tid[N];

template <typename T>
struct Fenwick {
    int n;
    std::vector<T> a;
    
    Fenwick(int n_ = 0) {
        init(n_);
    }
    
    void init(int n_) {
        n = n_;
        a.assign(n + 5, T{});
    }
    
    void upd(int x, const T &v) {
        for (int i = x; i <= n; i += i & -i) {
            a[i] = a[i] + v;
        }
    }
    
    T get(int x) {
        T ans{};
        for (int i = x; i > 0; i -= i & -i) {
            ans = ans + a[i];
        }
        return ans;
    }
    
    T get(int l, int r) {
        return get(r) - get(l - 1);
    }
    
    int kth(const T &k) {
        int x = 0;
        T cur{};
        for (int i = 20; i >= 0; i--) {
            if (x + (1 << i) <= n && cur + a[x + (1 << i)] < k) {
                x += (1 << i);
                cur = cur + a[x];
            }
        }
        return x + 1;
    }
};

Fenwick<int> bit;
bool vis[N];
vector<int> nxt;

void dfs(int i, int pre){   
    for(auto &[x, id] : adj[i]){
        if(x == pre) continue;
        id = ++ee;
        p[x] = i, dfs(x, i);
    }
}

void dfs2(int i){
    for(int j = (pt[i] + 1) % adj[i].size(); ; j = (j + 1) % adj[i].size()){
        if(j == pt[i] && i > 1) break;
        int x = adj[i][j].first;
        vid[++timedfs] = x, eid[timedfs] = adj[i][j].second;
        dfs2(x); 
        vid[++timedfs] = i, eid[timedfs] = adj[i][j].second;
        if(j == pt[i] && i == 1) break;
    }
}

void dfs3(int i){
    while(true){
        pt[i] = (pt[i] + 1) % adj[i].size();
        int j = pt[i], x = adj[i][j].first, ee = adj[i][j].second;
        if(vis[ee]) break;
        if(x == p[i]){
            nxt.push_back(i);
            break;
        }
        bit.upd(tid[ee][0], 1);
        bit.upd(tid[ee][1], 1);
        s += 2;
        dfs3(x);
        vis[ee] = true;
    }
}
void solve(){
    cin >> n >> q;
    for(int i = 1; i <= n; i++){
        int sz; cin >> sz;
        for(int j = 0; j < sz; j++){
            int x; cin >> x;
            adj[i].push_back({x, 0});
        }
    }
    dfs(1, 1);
    for(int i = 2; i <= n; i++){
        for(int j = 0; j < (int) adj[i].size(); j++){
            if(adj[i][j].first == p[i]) pt[i] = j;
        }
    }
    dfs2(1);  
    bit.init(timedfs);
    memset(pt, 0, sizeof pt);
    vector<pii> b;
    for(int i = 1; i <= q; i++){
        int x; cin >> x; b.push_back({x, i});
    }
    sort(b.begin(), b.end());
    for(int i = 1; i <= timedfs; i++) tid[eid[i]].push_back(i);
    queue<int> qu; qu.push(1);
    int total = 0, qid = 0;
    while(s < timedfs){
        nxt.clear();
        int last = total;
        while(!qu.empty()){
            dfs3(qu.front());
            qu.pop();
        }
        for(int x : nxt){
            qu.push(x);
        }
        total += s;
        while(qid < b.size() && b[qid].first <= total){
            ans[b[qid++].second] = vid[bit.kth(b[qid].first - last)];
        }
    }
    while(qid < b.size()){
        ans[b[qid].second] = vid[(b[qid].first - total - 1) % timedfs + 1];
    }
    for(int i = 1; i <= q; i++) cout << ans[i] << '\n';
}

signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    #define task "MAZE"
    if(fopen(task ".inp", "r")){
        freopen(task ".inp", "r", stdin);
        freopen(task ".out", "w", stdout);
    }  
    solve();
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:150:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  150 |         freopen(task ".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:151:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  151 |         freopen(task ".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 4
• Subtask 2: 0 / 4
• Subtask 3: 0 / 12
• Subtask 4: 0 / 5