Submission #687365

#	Time	Username	Problem	Language	Result	Execution time	Memory
687365		JooDdae	Regions (IOI09_regions)	C++17	60 / 100	3697 ms	131072 KiB

regions

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

const int B = 160;

int n, r, q, h[200200], p[200200];
int sz[200200], in[200200], out[200200], cnt, lev[200200], head[200200], rev[200200];

vector<int> v[200200], rv[30030], lb[30030];

int dfs_size(int u) {
    for(auto &x : v[u]) {
        sz[u] += dfs_size(x);
        if(sz[x] > sz[v[u][0]]) swap(x, v[u][0]);
    }
    return ++sz[u];
}

void dfs_hld(int u) {
    in[u] = ++cnt, lev[u] = lev[p[u]]+1;
    for(auto x : v[u]) {
        head[x] = (x == v[u][0] ? head[u] : x);
        dfs_hld(x);
    }
    out[u] = cnt;
}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    cin >> n >> r >> q >> h[1];
    for(int i=2;i<=n;i++) cin >> p[i] >> h[i];
    
    for(int i=1;i<=n;i++) v[p[i]].push_back(i);
    head[1] = 1, dfs_size(1), dfs_hld(1);
    for(int i=1;i<=n;i++) rv[h[i]].push_back(in[i]), rev[in[i]] = i;
    for(int i=1;i<=r;i++) sort(rv[i].begin(), rv[i].end());

    for(int i=1;i<=r;i++) if(rv[i].size() >= B) {
        lb[i].resize(n+1, 0);
        for(int j=0, k=0;j<=n;j++) {
            while(k < rv[i].size() && rv[i][k] <= j) k++;
            lb[i][j] = k;
        }
    }

    map<pair<int, int>, int> mp;
    while(q--) {
        int a, b; cin >> a >> b;

        if(mp.count({a, b})) { cout << mp[{a, b}] << endl; continue; }

        auto &ans = mp[{a, b}];
        if(rv[a].size() <= rv[b].size()) {
            for(auto x : rv[a]) {
                int L = x, R = out[rev[x]];
                if(!lb[b].empty()) ans += lb[b][R]-lb[b][L-1];
                else for(auto y : rv[b]) if(L <= y && y <= R) ans++;
            }
        } else {
            for(auto x : rv[b]) {
                int u = rev[x];
                while(u) {
                    int L = in[head[u]], R = in[u]; u = p[head[u]];
                    if(!lb[a].empty()) ans += lb[a][R]-lb[a][L-1];
                    else for(auto y : rv[a]) if(L <= y && y <= R) ans++;
                }
            }
        }

        cout << ans << endl;
    }
}

Compilation message (stderr)

regions.cpp: In function 'int main()':
regions.cpp:42:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |             while(k < rv[i].size() && rv[i][k] <= j) k++;
      |                   ~~^~~~~~~~~~~~~~

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