Submission #490620

#	Time	Username	Problem	Language	Result	Execution time	Memory
490620		dooompy	Regions (IOI09_regions)	C++11	100 / 100	3373 ms	112868 KiB

regions

#include "bits/stdc++.h"

using namespace std;

using ll = long long;

#define MAXN 200005
#define MAXR 25005
#define INF (long long)1e18
#define BLOCK 450

int n, r, q;
vector<int> region(MAXN);
vector<vector<int>> adj(MAXN);
int timer = 1;
int tin[MAXN], tout[MAXN];
vector<vector<int>> sorted(MAXR); // sorted[r] stores the nodes from region r in sorted order of {tin, tout}
vector<int> ind(MAXR);
vector<vector<int>> par(BLOCK, vector<int>(MAXR));
vector<vector<int>> child(BLOCK, vector<int>(MAXR));
vector<int> largeRegions;

void dfs(int i) {
    tin[i] = timer++;
    sorted[region[i]].push_back(i);

    for (auto a: adj[i]) {
        dfs(a);
    }

    tout[i] = timer - 1;
}

void genPar(int curr, int originalReg, int cnt) {
    par[ind[originalReg]][region[curr]] += cnt;
    cnt += (region[curr] == originalReg);

    for(auto child : adj[curr]) {
        genPar(child, originalReg, cnt);
    }
}

// Get answer for (a, b), sz[a] <= BLOCK, sz[b] > BLOCK

int genChild(int curr, int originalReg) {
    int sub = (region[curr] == originalReg);

    for(auto child : adj[curr]) {
        sub += genChild(child, originalReg);
    }

    child[ind[originalReg]][region[curr]] += sub;
    return sub;
}

bool isAnc(int a, int b) {
    return tin[a] <= tin[b] && tout[b] <= tout[a];
}

int getAns(int reg1, int reg2) {
    int l = 0, r = 0;
    int ans = 0;
    stack<int> st;

    while (l < sorted[reg1].size() || r < sorted[reg2].size()) {
        if ((l < sorted[reg1].size()) && (r == sorted[reg2].size() || tin[sorted[reg1][l]] < tin[sorted[reg2][r]])) {
            while (!st.empty() && !isAnc(st.top(), sorted[reg1][l])) {
                st.pop();
            }

            st.push(sorted[reg1][l]);
            l++;
        } else {
            while (!st.empty() && !isAnc(st.top(), sorted[reg2][r])) {
                st.pop();
            }

            ans += st.size();
            r++;
        }
    }

    return ans;
}



int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
//    freopen("", "r", stdin);
//    freopen("", "w", stdout);
    int n, r, q; cin >> n >> r >> q;
    cin >> region[1];

    for (int i = 2; i <= n; i++) {
        int s; cin >> s >> region[i];
        adj[s].push_back(i);
    }

    dfs(1);

    int idx = 0;

    for (int i = 1; i <= r; i++) {
        if (sorted[i].size() > BLOCK) {
            largeRegions.push_back(i);
            ind[i] = idx++;
        }
    }

    for (auto a : largeRegions) {
        genPar(1, a, 0);
        genChild(1, a);
    }

    for (int i = 0; i < q; i++) {
        int a, b; cin >> a >> b;

        if (sorted[a].size() <= BLOCK && sorted[b].size() <= BLOCK) {
            cout << getAns(a, b) << endl;
            continue;
        }

        if (sorted[a].size() > BLOCK) {
            cout << par[ind[a]][b] << endl;
        } else {
            cout << child[ind[b]][a] << endl;
        }
    }
}

Compilation message (stderr)

regions.cpp: In function 'int getAns(int, int)':
regions.cpp:65:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   65 |     while (l < sorted[reg1].size() || r < sorted[reg2].size()) {
      |            ~~^~~~~~~~~~~~~~~~~~~~~
regions.cpp:65:41: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   65 |     while (l < sorted[reg1].size() || r < sorted[reg2].size()) {
      |                                       ~~^~~~~~~~~~~~~~~~~~~~~
regions.cpp:66:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   66 |         if ((l < sorted[reg1].size()) && (r == sorted[reg2].size() || tin[sorted[reg1][l]] < tin[sorted[reg2][r]])) {
      |              ~~^~~~~~~~~~~~~~~~~~~~~
regions.cpp:66:45: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   66 |         if ((l < sorted[reg1].size()) && (r == sorted[reg2].size() || tin[sorted[reg1][l]] < tin[sorted[reg2][r]])) {
      |                                           ~~^~~~~~~~~~~~~~~~~~~~~~

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