Submission #796168

#	Time	Username	Problem	Language	Result	Execution time	Memory
796168		_martynas	Split the Attractions (IOI19_split)	C++14	100 / 100	89 ms	20196 KiB

split

#include "split.h"
#include <algorithm>
#include <iostream>

using namespace std;

const int mxn = 1e5+5;

bool visited[mxn];
int sz[mxn];
vector<int> par;
vector<int> color, adj[mxn];
vector<pair<int, int>> new_edges;

void dfs(int u) {
    visited[u] = true;
    sz[u] = 1;
    for(int v : adj[u]) if(!visited[v]) {
        par[v] = u;
        new_edges.push_back({u, v});
        dfs(v); sz[u] += sz[v];
    }
}

int find_centroid(int u, int n) {
    visited[u] = true;
    for(int v : adj[u]) if(!visited[v] && 2*sz[v]>n) {
        return find_centroid(v, n);
    }
    return u;
}

void mark(int u, int m, vector<int> &where, int &cnt) {
    if(cnt <= 0) return;
    visited[u] = true;
    where[u] = m;
    cnt--;
    for(int v : adj[u]) if(!visited[v]) {
        mark(v, m, where, cnt);
    }
}

int get_par(int u) {
    return par[u] == u ? u : par[u] = get_par(par[u]);
}

bool join(int u, int v) {
    u = get_par(u), v = get_par(v);
    if(u == v) return false;
    if(sz[u] < sz[v]) swap(u, v);
    sz[u] += sz[v];
    par[v] = u;
    return true;
}

vector<int> find_split(int n, int a, int b, int c, vector<int> p, vector<int> q) {
    for(int i = 0; i < p.size(); i++) {
        int u = p[i], v = q[i];
        adj[u].push_back(v), adj[v].push_back(u);
    }
    par.resize(n, -1);
    dfs(0);
    for(int i = 0; i < n; i++) {
        adj[i].clear();
    }
    for(auto e : new_edges) {
        adj[e.first].push_back(e.second);
        adj[e.second].push_back(e.first);
    }
    fill(visited, visited+n, false);
    int centroid = find_centroid(0, n);
    vector<pair<int, int>> groups = {pair<int, int>{a, 1}, pair<int, int>{b, 2}, pair<int, int>{c, 3}};
    sort(groups.begin(), groups.end());
	color.resize(n, groups[2].second);
    int small_group = -1;
    int cnt;
    if(par[centroid] != -1) sz[par[centroid]] = n-sz[centroid];
    // continue adding non-tree edges until max sz exceeds min(a, b, c)
    // or the edges run out
    int mx = 0;
    // current maximum
    for(int u : adj[centroid]) mx = max(mx, sz[u]);
    // initial parents (set sizes are equivalent to subtree ones)
    fill(visited, visited+n, false);
    visited[centroid] = true;
    for(int u : adj[centroid]) {
        cnt = mxn;
        mark(u, u, par, cnt);
    }
    // adding edges
    for(int i = 0; i < p.size() && mx < groups[0].first; i++) {
        if(p[i] != centroid && q[i] != centroid && join(p[i], q[i])) {
            adj[p[i]].push_back(q[i]);
            adj[q[i]].push_back(p[i]);
            mx = max(mx, sz[get_par(p[i])]);
        }
    }
    if(mx < groups[0].first) return vector<int>(n, 0);
    fill(visited, visited+n, false);
    for(int u : adj[centroid]) {
        if(sz[u] >= groups[0].first) {
            visited[centroid] = true;
            cnt = groups[0].first;
            mark(u, groups[0].second, color, cnt);
            small_group = u;
            break;
        }
    }
    cnt = groups[1].first;
    mark(centroid, groups[1].second, color, cnt);
	return color;
}

Compilation message (stderr)

split.cpp: In function 'std::vector<int> find_split(int, int, int, int, std::vector<int>, std::vector<int>)':
split.cpp:57:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   57 |     for(int i = 0; i < p.size(); i++) {
      |                    ~~^~~~~~~~~~
split.cpp:91:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   91 |     for(int i = 0; i < p.size() && mx < groups[0].first; i++) {
      |                    ~~^~~~~~~~~~
split.cpp:75:9: warning: variable 'small_group' set but not used [-Wunused-but-set-variable]
   75 |     int small_group = -1;
      |         ^~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 11 / 11
• Subtask 3: 22 / 22
• Subtask 4: 24 / 24
• Subtask 5: 36 / 36