Submission #1280085

#	Time	Username	Problem	Language	Result	Execution time	Memory
1280085		Aquarius	Regions (IOI09_regions)	C++20	60 / 100	8042 ms	43692 KiB

regions

#include<bits/stdc++.h>
#define int long long
#define sz(x) (int) x.size()
#define all(x) x.begin(), x.end()
using namespace std;



const int N = 2e5 + 5;

const int BLOCK = sqrt(N);

vector<int> E[N];
vector<int> can_st[N], can_ed[N];
vector<int> group[N];

int ans[BLOCK][25000];

int group_id[N];


int val[N], st[N], ed[N];
int n, q, r, t = 0;

void dfs(int u, int p) {
    st[u] = ++t;
    can_st[val[u]].push_back(st[u]);
    for(int v: E[u]) {
        if(v==p) continue;
        dfs(v, u);
    }
    ed[u] = ++t;
    can_ed[val[u]].push_back(ed[u]);
}


int count_parent(int u, int c) {
    // st[x] <= st[u]
    // ed[x] <= st[u]

    int a =  upper_bound(all(can_st[c]), st[u]) - can_st[c].begin();
    int b =  upper_bound(all(can_ed[c]), st[u]) - can_ed[c].begin();
    return a - b;
}

void solve() {
    cin >> n >> r >> q;
    for(int i=1; i<=n; i++) {
        if(i != 1) {
            int p; cin >> p;
            E[p].push_back(i);
            E[i].push_back(p);
        }
        cin >> val[i];
        group[val[i]].push_back(i);
    }

    dfs(1, 0);
    for(int i=1; i<=r; i++) sort(all(can_ed[i]));



    for(int i=1, cnt = 0, id; i<=n; i++) {
        if(sz(group[val[i]]) <= BLOCK) continue;

        if(group_id[val[i]] == 0) {
            id = ++cnt;
            group_id[val[i]] = id;
        }
        else id = group_id[val[i]];

        for(int color = 1; color <=r; color++) {
            if(color == val[i]) continue;
            ans[id][color] += count_parent(i, color);
        }

    }



    while(q--) {
        int r1, r2;  cin >> r1 >> r2;
        if(sz(group[r2]) <= BLOCK) {
            int tot = 0;
            for(int u: group[r2]) {
                tot += count_parent(u, r1);
            }
            cout<< tot <<endl;
        }
        else cout<<ans[group_id[r2]][r1] << endl;
    }


}

/*
1
3
2
1
*/
signed main() {
    if(fopen("input.txt", "r")) freopen("input.txt", "r", stdin);
    ios_base::sync_with_stdio(false);cin.tie(0);
    int T = 1;
//    cin >> T;
    while(T--) solve();
}

Compilation message (stderr)

regions.cpp: In function 'int main()':
regions.cpp:103:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  103 |     if(fopen("input.txt", "r")) freopen("input.txt", "r", stdin);
      |                                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 15 / 15
• Subtask 2: 45 / 85