Submission #1185235

#	Time	Username	Problem	Language	Result	Execution time	Memory
1185235		kl0989e	Village (BOI20_village)	C++20	56 / 100	88 ms	27208 KiB

Village

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

#define ll long long
#define fi first
#define se second
#define pb push_back
#define vi vector<int>
#define vl vector<ll>
#define pi pair<int, int>
#define pl pair<ll,ll>
#define all(x) (x).begin(),(x).end()

const int maxn=1e5+10;
int n;

vector<vi> graph(maxn);
vi sze(maxn,1);

void dfs(int cur, int prev=-1) {
	for (auto to:graph[cur]) {
		if (to==prev) {
			continue;
		}
		dfs(to,cur);
		sze[cur]+=sze[to];
	}
}

vector<vi> dp(maxn,vi(2,1e9));
vi to(maxn,-1);

void dfs2(int cur, int prev=-1) {
	if (graph[cur].size()==1 && cur!=0) {
		dp[cur][1]=0;
		return;
	}
	int cnt=0;
	int diff=1e9;
	for (auto to:graph[cur]) {
		if (to==prev) {
			continue;
		}
		dfs2(to,cur);
		cnt+=min(dp[to][0],dp[to][1]+2);
		if (dp[to][1]+2<=dp[to][0]) {
			diff=0;
		}
		else {
			diff=min(diff,dp[to][1]+2-dp[to][0]);
		}
	}
	dp[cur][1]=cnt;
	dp[cur][0]=cnt+diff;
}

pi dfs3(int ii, int cur, int prev=-1) {
	vector<pi> out={{cur,cur}};
	int t=-1;
	if (ii==0 && dp[cur][0]!=dp[cur][1]) {
		for (auto to:graph[cur]) {
			if (to==prev) {
				continue;
			}
			if (dp[to][1]+2-dp[to][0]==dp[cur][0]-dp[cur][1]) {
				t=to;
				break;
			}
		}
	}
	for (auto to:graph[cur]) {
		if (to==prev) {
			continue;
		}
		if (to==t || dp[to][1]+2<=dp[to][0]) {
			out.pb(dfs3(1,to,cur));
		}
		else {
			dfs3(0,to,cur);
		}
	}
	int prv=out.size()-1;
	for (int i=0; i<out.size(); i++) {
		to[out[i].fi]=out[prv].se;
		prv=i;
	}
	return {out[0].fi,to[out[0].fi]};
}

vi to2(maxn,0);

int dfs4(int cur, int prev=-1) {
	bool ok=1;
	for (auto to:graph[cur]) {
		if (to==prev) {
			continue;
		}
		int temp=dfs4(to,cur);
		if (temp!=-1) {
			return temp;
		}
		if (sze[to]>n/2) {
			ok=0;
		}
	}
	if (ok && n-sze[cur]<=n/2) {
		return cur;
	}
	return -1;
}

vector<vector<pi>> comp;

void dfs5(int cur, int prev=-1) {
	comp.back().pb({cur,cur});
	for (auto to:graph[cur]) {
		if (to==prev) {
			continue;
		}
		dfs5(to,cur);
	}
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
	cin >> n;
	int a,b;
	for (int i=0; i<n-1; i++) {
		cin >> a >> b;
		graph[--a].pb(--b);
		graph[b].pb(a);
	}
	dfs(0);
	dfs2(0);
	dfs3(0,0);
	int cen=dfs4(0);
	comp.pb({{cen,cen}});
	for (auto to:graph[cen]) {
		comp.pb({});
		dfs5(to,cen);
	}
	vi ord(comp.size());
	iota(all(ord),0);
	sort(all(ord),[&](int a, int b){return comp[a].size()>comp[b].size();});
	int pt1=0,pt2=1;
	pi temp={-1,-1};
	while (pt1<comp.size() && pt2<comp.size()) {
		while (pt1<comp.size() && comp[ord[pt1]].size()==0) {
			pt1++;
		}
		while (pt2<comp.size() && (comp[ord[pt2]].size()==0 || pt1==pt2)) {
			pt2++;
		}
		if (pt1==comp.size() || pt2==comp.size()) {
			break;
		}
		if (comp[ord[pt1]].size()<comp[ord[pt2]].size()) {
			swap(pt1,pt2);
		}
		while (comp[ord[pt2]].size()) {
			pi a=comp[ord[pt1]].back();
			comp[ord[pt1]].pop_back();
			pi b=comp[ord[pt2]].back();
			comp[ord[pt2]].pop_back();
			to2[a.fi]=b.se;
			to2[b.fi]=a.se;
			if (comp[ord[pt2]].size()==0) {
				temp={b.fi,a.se};
			}
		}
	}
	if (pt1<comp.size() && comp[ord[pt1]].size()) {
		pi a=comp[ord[pt1]].back();
		comp[ord[pt1]].pop_back();
		to2[a.fi]=temp.se;
		to2[temp.fi]=a.se;
	}
	if (pt2<comp.size() && comp[ord[pt2]].size()) {
		pi a=comp[ord[pt2]].back();
		comp[ord[pt2]].pop_back();
		to2[a.fi]=temp.se;
		to2[temp.fi]=a.se;
	}
	ll ans2=0;
	for (int i=1; i<n; i++) {
		ans2+=2*min(sze[i],n-sze[i]);
	}
	cout << dp[0][0] << ' ' << ans2 << '\n';
	for (int i=0; i<n; i++) {
		cout << to[i]+1 << " \n"[i==n-1];
	}
	for (int i=0; i<n; i++) {
		cout << to2[i]+1 << " \n"[i==n-1];
	}
    return 0;
}

• Subtask 1: 12 / 12
• Subtask 2: 19 / 38
• Subtask 3: 25 / 50