Submission #27221

#	Time	Username	Problem	Language	Result	Execution time	Memory
27221		top34051	Dreaming (IOI13_dreaming)	C++14	100 / 100	151 ms	19436 KiB

dreaming

#include<bits/stdc++.h>
#include "dreaming.h"
using namespace std;
#define maxn 100005
int head[maxn];
long long len[maxn];
pair<int,long long> rec[maxn];
vector<pair<int,long long> > from[maxn];
vector<int> p[maxn];
vector<long long> a;
void dfs(int x,int last,int dist) {
    int i;
    len[x] = len[last] + dist;
    rec[x] = {last, dist};
    for(i=0;i<from[x].size();i++) if(from[x][i].first!=last) dfs(from[x][i].first,x,from[x][i].second);
}
int findhead(int x) {
    if(head[x]==x) return x;
    return head[x] = findhead(head[x]);
}
bool cmp(int x,int y) {
    return x>y;
}
int travelTime(int N,int M,int L,int A[],int B[],int T[]) {
    int i,j,now;
    long long sum,full,half,ans;
    for(i=0;i<N;i++) head[i] = i;
    for(i=0;i<M;i++) from[A[i]].push_back({B[i],T[i]}), from[B[i]].push_back({A[i],T[i]}), head[findhead(A[i])] = findhead(B[i]);
    for(i=0;i<N;i++) p[findhead(i)].push_back(i);
    ans = 0;
    for(i=0;i<N;i++) {
        if(p[i].size()==0) continue;
        for(j=0;j<p[i].size();j++) len[p[i][j]] = 0;
        //First
        now = p[i][0];
        dfs(now,-1,0);
        //Second
        for(j=0;j<p[i].size();j++) if(len[p[i][j]]>len[now]) now = p[i][j];
        for(j=0;j<p[i].size();j++) len[p[i][j]] = 0;
        dfs(now,-1,0);
        //Track
        for(j=0;j<p[i].size();j++) if(len[p[i][j]]>len[now]) now = p[i][j];
        full = half = len[now]; sum = 0;
        while(now!=-1) {
            sum += rec[now].second;
            now = rec[now].first;
            half = min(half,max(sum,full-sum));
        }
        ans = max(ans,full);
        a.push_back(half);
    }
    sort(&a[0],&a[a.size()],cmp);
    if(a.size()>1) ans = max(ans,a[0]+a[1]+L);
    if(a.size()>2) ans = max(ans,a[1]+a[2]+L+L);
    return ans;
}

Compilation message (stderr)

dreaming.cpp: In function 'void dfs(int, int, int)':
dreaming.cpp:15:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(i=0;i<from[x].size();i++) if(from[x][i].first!=last) dfs(from[x][i].first,x,from[x][i].second);
             ~^~~~~~~~~~~~~~~
dreaming.cpp: In function 'int travelTime(int, int, int, int*, int*, int*)':
dreaming.cpp:33:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(j=0;j<p[i].size();j++) len[p[i][j]] = 0;
                 ~^~~~~~~~~~~~
dreaming.cpp:38:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(j=0;j<p[i].size();j++) if(len[p[i][j]]>len[now]) now = p[i][j];
                 ~^~~~~~~~~~~~
dreaming.cpp:39:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(j=0;j<p[i].size();j++) len[p[i][j]] = 0;
                 ~^~~~~~~~~~~~
dreaming.cpp:42:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(j=0;j<p[i].size();j++) if(len[p[i][j]]>len[now]) now = p[i][j];
                 ~^~~~~~~~~~~~

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