Submission #96983

#	Time	Username	Problem	Language	Result	Execution time	Memory
96983		E869120	Dreaming (IOI13_dreaming)	C++14	18 / 100	100 ms	20724 KiB

dreaming

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

vector<pair<int, int> >X[1<<18]; vector<int> J[1<<18], G;
int N, M, L, EA, EB, col[1<<18], cnts, dist[1<<18], dist2[1<<18];

void dfs(int pos){
	if(col[pos]>=1) return;
	col[pos]=cnts; J[cnts].push_back(pos);
	for(int i=0;i<X[pos].size();i++) dfs(X[pos][i].first);
}

void getdist(int pos){
	queue<int>que; que.push(pos); dist[pos]=0;
	
	while(!que.empty()){
		int p = que.front(); que.pop();
		for(int i=0;i<(int)X[p].size();i++) {
			int to = X[p][i].first;
			if(dist[to]>dist[p]+X[p][i].second){
				dist[to]=dist[p]+X[p][i].second;
				que.push(to);
			}
		}
	}
}

pair<int, int> radius(int pos){
	// 1. get dist(1, a)
	int cols = pos; pos = J[pos][0];
	
	for(int i=0;i<J[pos].size();i++) dist[J[pos][i]]=(1<<30);
	getdist(pos);
	
	int maxp=-1;
	for(int i:J[cols]){
		if(maxp<dist[i]) {maxp = dist[i]; pos = i;}
	}
	
	// 2. get dist(a, b)
	queue<int>que;
	for(int i=0;i<(int)J[cols].size();i++) dist2[J[cols][i]]=(1<<30);
	que.push(pos); dist2[pos]=0;
	
	while(!que.empty()){
		int p = que.front(); que.pop();
		for(int i=0;i<(int)X[p].size();i++) {
			int to = X[p][i].first;
			if(dist2[to]>dist2[p]+X[p][i].second){
				dist2[to]=dist2[p]+X[p][i].second;
				que.push(to);
			}
		}
	}
	
	int ans=-1; EA=pos;
	for(int i:J[cols]) {
		if(ans<dist2[i]){ans=dist2[i];EB=i;}
	}
	
	// 3. get dist(b, a)
	for(int i:J[cols]) dist[i]=(1<<30);
	getdist(EB);
	
	int ans2=ans;
	for(int i:J[cols]){
		if(dist[i]+dist2[i]==dist2[EB]) ans2 = min(ans2, max(dist[i], dist2[i]));
	}
	return make_pair(ans, ans2);
}

int travelTime(int NN, int MM, int LL, int A[], int B[], int T[]) {
    N = NN; M = MM; L = LL;
    for(int i=0;i<M;i++){
		X[A[i]].push_back(make_pair(B[i], T[i]));
		X[B[i]].push_back(make_pair(A[i], T[i]));
	}
	for(int i=1;i<=N;i++){
		if(col[i]>=1) continue;
		cnts++;dfs(i);
	}
	
	int maxn=0;
	for(int i=1;i<=cnts;i++){
		pair<int, int>I1 = radius(i); maxn = max(maxn, I1.first);
		//cout<<i<<":"<<I1.first<<" "<<I1.second<<endl;
		G.push_back(I1.second);
	}
	sort(G.begin(), G.end());
	reverse(G.begin(), G.end());
	
	if(G.size()==1) return maxn;
	
	int rem=(1<<30);
	for(int i=0;i<(int)G.size();i++){
		int v1 = G[i]; vector<int>v2;
		for(int j=0;j<(int)G.size();j++){
			if(j != i) v2.push_back(G[j]);
			if(v2.size()==2) break;
		}
		int s1 = v1 + v2[0] + L;
		int s2 = 0; if(v2.size()==2) s2 = v2[0] + v2[1] + L * 2;
		rem = min(rem, max(s1, s2));
	}
	return max(maxn, rem);
}

Compilation message (stderr)

dreaming.cpp: In function 'void dfs(int)':
dreaming.cpp:11:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<X[pos].size();i++) dfs(X[pos][i].first);
              ~^~~~~~~~~~~~~~
dreaming.cpp: In function 'std::pair<int, int> radius(int)':
dreaming.cpp:33:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<J[pos].size();i++) dist[J[pos][i]]=(1<<30);
              ~^~~~~~~~~~~~~~

• Subtask 1: 0 / 14
• Subtask 2: 0 / 10
• Subtask 3: 0 / 23
• Subtask 4: 18 / 18
• Subtask 5: 0 / 12
• Subtask 6: 0 / 23