Submission #793499

#	Time	Username	Problem	Language	Result	Execution time	Memory
793499		phoebe	Regions (IOI09_regions)	C++17	100 / 100	4872 ms	79304 KiB

regions

#include <bits/stdc++.h>
using namespace std;
 
#pragma GCC optimize("03")
 
// #define int long long
#define ll long long
#define pii pair<int, int>
#define F first
#define S second
#define PB push_back
#define ALL(x) x.begin(), x.end()
#define FOR(i, n) for (int i = 0; i < n; i++)
#define NYOOM ios::sync_with_stdio(0); cin.tie(0);
// #define endl '\n'
const int INF = 1e9 + 7;
const ll LLINF = 1ll<<60;
 
const int maxn = 2e5 + 10, block = 400, maxr = 25005;
int n, r, q, h[maxn], arrive[maxn], leave[maxn], 
cnt[maxn / block][maxr] = {0}, // cnt[i][j] = # region i as manager of j
timer = 0, cur[block] = {0}, get_idx[maxn], idx = 0;
vector<int> adj[maxn], bruh[maxr], // bruh[i] = vector of arrive time of region i
region[maxr]; // region[i] = vector of all nodes in region i
 
void dfs(int v){ // O(n sqrt n)
    arrive[v] = timer++;
    bruh[h[v]].PB(arrive[v]);
    FOR(i, maxn / block) cnt[i][h[v]] += cur[i];
    if (get_idx[h[v]] != -1) cur[get_idx[h[v]]]++;
    for (auto u : adj[v]){
        dfs(u);
    }
    if (get_idx[h[v]] != -1) cur[get_idx[h[v]]]--;
    leave[v] = timer++;
}
 
signed main(){
    NYOOM;
    fill(get_idx, get_idx + maxn, -1);
    cin >> n >> r >> q;
    cin >> h[1]; region[h[1]].PB(1);
    for (int i = 2; i <= n; i++){
        int s; cin >> s >> h[i];
        adj[s].PB(i); region[h[i]].PB(i);
    }
    for (int i = 1; i <= r; i++){
        if (region[i].size() >= block) get_idx[i] = idx++;
    }
    dfs(1);
    FOR(i, q){
        int r1, r2; cin >> r1 >> r2;
        if (get_idx[r1] != -1){
            cout << cnt[get_idx[r1]][r2] << endl;
            continue;
        }
        int re = 0;
        for (auto v : region[r1]){ // o(sqrt n log n)
            int l = lower_bound(ALL(bruh[r2]), arrive[v]) - bruh[r2].begin();
            int r = lower_bound(ALL(bruh[r2]), leave[v]) - bruh[r2].begin();
            // cout << l << ' ' << r << endl; 
            re += r - l;
        }
        cout << re << endl;
    }
    // total = o(n sqrt n + q sqrt n log n)
}

Compilation message (stderr)

regions.cpp: In function 'void dfs(int)':
regions.cpp:29:47: warning: iteration 400 invokes undefined behavior [-Waggressive-loop-optimizations]
   29 |     FOR(i, maxn / block) cnt[i][h[v]] += cur[i];
      |                                          ~~~~~^
regions.cpp:13:37: note: within this loop
   13 | #define FOR(i, n) for (int i = 0; i < n; i++)
......
   29 |     FOR(i, maxn / block) cnt[i][h[v]] += cur[i];
      |         ~~~~~~~~~~~~~~~              
regions.cpp:29:5: note: in expansion of macro 'FOR'
   29 |     FOR(i, maxn / block) cnt[i][h[v]] += cur[i];
      |     ^~~

• Subtask 1: 15 / 15
• Subtask 2: 85 / 85