Submission #1047783

#	Time	Username	Problem	Language	Result	Execution time	Memory
1047783		MercubytheFirst	Split the Attractions (IOI19_split)	C++14	0 / 100	1 ms	348 KiB

split

#include <bits/stdc++.h>
#include "split.h"
using namespace std;
using pii = pair<int, int>;

vector<int> tin, low, root, val;
int timer;
vector<vector<pii> > g;
vector<vector<int> > cg, components(1);
int comp_cnt = 0;
vector<bool> vis;

vector<bool> is_bridge;


vector<int> sub;
pair<int, int> sz[3];
int cnt[3];
int ansv = -1, ansp = -1;

int sub_dfs(int v, int p) {
	sub[v] = val[v];
	for(int to : cg[v]) {
		if(to != p) {
			sub[v] += sub_dfs(to, v);
		}
	}
	return sub[v];
}

void finder_dfs(int v, int p) {
	if(ansv != -1) {
		return;
	}
	const int subtree = sub[v]-val[v], uptree = sub[0] - sub[v];
	const int diff = max(0, sz[0].first - min(subtree, uptree)) + max(0, sz[1].first - max(subtree, uptree));
	if(diff <= val[v]) {
		ansv = v;
		ansp = p;
		return;
	}
	for(int to : cg[v]) {
		if(to != p) {
			finder_dfs(to, v);
			if(ansv != -1) {
				return;
			}
		}
	}
}

void bridge_dfs(int v, int p) {
	assert(!vis[v]);
	vis[v] = true;
	tin[v] = low[v] = ++timer;
	for(auto e : g[v]) {
		int to = e.first, idx = e.second;
		if(to == p) {
			continue;
		}
		if(!vis[to]) {
			bridge_dfs(to, v);
			if(low[to] > tin[v]) {
				// cout << v << ' ' << to << endl;
				is_bridge[idx] = true;
			}
			low[v] = min(low[v], low[to]);
		}
		else {
			low[v] = min(low[v], low[to]);
		}
	}
}

void comp_dfs(int v, int cur_comp) {
	assert(!vis[v]);
	vis[v] = true;
	root[v] = cur_comp;
	components[cur_comp].push_back(v);
	val[cur_comp]++;
	for(const auto& e : g[v]) {
		int to = e.first, idx = e.second;
		if(vis[to]) {
			continue;
		}
		if(is_bridge[idx]) {
			comp_cnt++;
			components.emplace_back();
			comp_dfs(to, comp_cnt);
		}
		else {
			comp_dfs(to, cur_comp);
		}
	}
}


void finalize_dfs(vector<int>& res, int v, int p, int group) {
	if(cnt[group] >= sz[group].first) {
		assert(cnt[group] <= sz[group].first);
		return;
	}
	assert(!res[v]);
	assert(0 <= group and group < 3);
	res[v] = sz[group].second;
	cnt[group]++;
	for(const auto& e : g[v]) {
		int to = e.first, idx = e.second;
		if(root[to] == p or res[to] != 0) {
			continue;
		}
		finalize_dfs(res, to, v, group);
		if(cnt[group] >= sz[group].first) {
			assert(cnt[group] <= sz[group].first);
			return;
		}
	}
}

void bounded_dfs(vector<int>& res, int v, int group) {
	if(cnt[group] >= sz[group].first) {
		assert(cnt[group] <= sz[group].first);
		return;
	}
	assert(!res[v]);
	assert(0 <= group and group < 3);
	res[v] = sz[group].second;
	cnt[group]++;
	for(const auto& e : g[v]) {
		int to = e.first, idx = e.second;
		if(root[to] != root[v] or res[to] != 0) {
			continue;
		}
		finalize_dfs(res, to, v, group);
		if(cnt[group] >= sz[group].first) {
			assert(cnt[group] <= sz[group].first);
			return;
		}
	}
}

vector<signed> find_split(signed n, signed a, signed b, signed c, vector<signed> p, vector<signed> q) {
	vector<signed> res(n);
	int m = p.size();
	sub.assign(n, 0);
	val.assign(n, 0);
	g.assign(n, vector<pii>());
	vis.assign(n, false);
	tin.assign(n, -1);
	low.assign(n, -1);
	root.assign(n, -1);
	is_bridge.assign(m, false);
	for(int i = 0; i < m; ++i) {
		const int u = p[i];
		const int v = q[i];
		g[u].push_back({v, i});
		g[v].push_back({u, i});
	}
	bridge_dfs(0, -1);
	vis.assign(n, false);
	comp_dfs(0, comp_cnt);
	cg.assign(comp_cnt + 3, vector<int>());
	for(int u = 0; u < n; ++u) {
		for(const auto& e : g[u]) {
			int v = e.first;
			assert(root[u] != -1 and root[v] != -1);
			if(root[u] == root[v]) {
				continue;
			}
			cg[root[u]].push_back(root[v]);
		}
	}
	sub_dfs(0, -1);
	finder_dfs(0, -1);
	// cout << ansv << ' ' << ansp << endl;
	if(ansv == -1) {
		// cout << "Hi";
		assert(ansp == -1);
		return res;
	}
	const int subtree = sub[ansv]-val[ansv], uptree = sub[0] - sub[ansv];
	if(subtree < uptree) {
		for(int child : cg[ansv]) {
			if(child == ansp) {
				continue;
			}
			finalize_dfs(res, components[child].back(), ansv, 0);
		}
		if(ansp != -1) {
			finalize_dfs(res, ansp, ansv, 1);
		}
	}
	else {
		for(int child : cg[ansv]) {
			if(child == ansp) {
				continue;
			}
			finalize_dfs(res, components[child].back(), ansv, 1);
		}
		if(ansp != -1) {
			finalize_dfs(res, ansp, ansv, 0);
		}
	}
	for(int v : components[ansv]) {
		if(!res[v]) {
			bounded_dfs(res, v, 0);
			break;
		}
	}
	for(int v : components[ansv]) {
		if(!res[v]) {
			bounded_dfs(res, v, 1);
			break;
		}
	}
	return res;
}


/*
6 5
1 3 2
0 1      
0 2
0 3
0 4
0 5

9 10
3 3 3
0 1
0 2
0 3
0 4
0 6
0 8
1 7
3 7
4 5
5 6

*/

Compilation message (stderr)

split.cpp: In function 'void finalize_dfs(std::vector<int>&, int, int, int)':
split.cpp:108:21: warning: unused variable 'idx' [-Wunused-variable]
  108 |   int to = e.first, idx = e.second;
      |                     ^~~
split.cpp: In function 'void bounded_dfs(std::vector<int>&, int, int)':
split.cpp:130:21: warning: unused variable 'idx' [-Wunused-variable]
  130 |   int to = e.first, idx = e.second;
      |                     ^~~

• Subtask 1: 0 / 7
• Subtask 2: 0 / 11
• Subtask 3: 0 / 22
• Subtask 4: 0 / 24
• Subtask 5: 0 / 36