Submission #115295

#	Time	Username	Problem	Language	Result	Execution time	Memory
115295		suzy	Dreaming (IOI13_dreaming)	C++17	59 / 100	1064 ms	18024 KiB

dreaming

#include <stdio.h>
#include <string.h>
#include <queue>
#include <vector>
#include <algorithm>
#include "dreaming.h"

using namespace std;

class e {
public:
	int v, w;
	e(int v, int w)
	:v(v),w(w)
	{}
};

vector<e> con[100001];
int n, m, l, d[100001];
bool vis[100001];
vector<int> comp[100001];
int k;

int solve(int pre, int u, int up) {
	int mx1=up, mx2=-1, v1=-1, v2=-1;
	for(int i=0;i<con[u].size();i++) {
		int v=con[u][i].v, w=con[u][i].w;
		if(pre==v) continue;
		if(d[v]+w>=mx1) {
			mx2=mx1;
			v2=v1;
			mx1=d[v]+w;
			v1=v;
		} else if(d[v]+w>mx2) {
			mx2=d[v]+w;
			v2=v;
		}
	}
	int ret=mx1;
	for(int i=0;i<con[u].size();i++) {
		int v=con[u][i].v, w=con[u][i].w;
		if(pre==v) continue;
		if(v==v1) ret=min(ret,solve(u,v,mx2+w));
		else ret=min(ret,solve(u,v,mx1+w));
	}
	return ret;
}

void dfs(int pre, int u) {
	comp[k].push_back(u);
	vis[u]=true;
	for(int i=0;i<con[u].size();i++) {
		int v=con[u][i].v, w=con[u][i].w;
		if(pre==v) continue;
		dfs(u,v);
		d[u]=max(d[u],d[v]+w);
	}
}

int dia(int u, bool fst, int c) {
	if(c<0) memset(d,-1,sizeof(d));
	else {
		for(int i=0;i<comp[c].size();i++)
			d[comp[c][i]]=-1;
	}
	queue<int> q;
	q.push(u);
	d[u]=0;
	while(!q.empty()) {
		int u=q.front();
		q.pop();
		for(int i=0;i<con[u].size();i++) {
			int v=con[u][i].v, w=con[u][i].w;
			if(d[v]<0) {
				d[v]=d[u]+w;
				q.push(v);
			}
		}
	}
	int mx=-1, tar;
	for(int i=1;i<=n;i++) {
		if(d[i]>mx) {
			mx=d[i]; tar=i;
		}
	}
	if(fst) return dia(tar,false,c);
	else return mx;
}

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
	n=N; m=M; l=L;
	for(int i=0;i<m;i++) {
		int u, v, w;
		u=A[i]; v=B[i]; w=T[i];
		u++; v++;
		con[u].push_back(e(v,w));
		con[v].push_back(e(u,w));
	}
	if(m==n-1) {
		return dia(1,true,-1);
	}
	vector<int> rt;
	for(int i=1;i<=n;i++) if(!vis[i]) {
		rt.push_back(i);
		dfs(-1,i);
		k++;
	}
	vector<int> v;
	for(int i=0;i<rt.size();i++)
		v.push_back(solve(-1,rt[i],0));
	sort(v.begin(),v.end());
	for(int i=0;i<v.size()-1;i++) v[i]+=l;
	sort(v.begin(),v.end());
	int ret=v.back()+v[v.size()-2];
	for(int i=0;i<rt.size();i++)
		ret=max(ret,dia(rt[i],true,i));
	return ret;
}

Compilation message (stderr)

dreaming.cpp: In function 'int solve(int, int, int)':
dreaming.cpp:26:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<con[u].size();i++) {
              ~^~~~~~~~~~~~~~
dreaming.cpp:40:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<con[u].size();i++) {
              ~^~~~~~~~~~~~~~
dreaming.cpp:25:29: warning: variable 'v2' set but not used [-Wunused-but-set-variable]
  int mx1=up, mx2=-1, v1=-1, v2=-1;
                             ^~
dreaming.cpp: In function 'void dfs(int, int)':
dreaming.cpp:52:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<con[u].size();i++) {
              ~^~~~~~~~~~~~~~
dreaming.cpp: In function 'int dia(int, bool, int)':
dreaming.cpp:63:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<comp[c].size();i++)
               ~^~~~~~~~~~~~~~~
dreaming.cpp:72:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<con[u].size();i++) {
               ~^~~~~~~~~~~~~~
dreaming.cpp: In function 'int travelTime(int, int, int, int*, int*, int*)':
dreaming.cpp:109:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<rt.size();i++)
              ~^~~~~~~~~~
dreaming.cpp:112:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<v.size()-1;i++) v[i]+=l;
              ~^~~~~~~~~~~
dreaming.cpp:115:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<rt.size();i++)
              ~^~~~~~~~~~
dreaming.cpp: In function 'int dia(int, bool, int)':
dreaming.cpp:86:32: warning: 'tar' may be used uninitialized in this function [-Wmaybe-uninitialized]
  if(fst) return dia(tar,false,c);
                                ^

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