Submission #167494

#	Time	Username	Problem	Language	Result	Execution time	Memory
167494		DavidDamian	Dreaming (IOI13_dreaming)	C++11	77 / 100	1073 ms	10972 KiB

dreaming

#include "dreaming.h"
#include<vector>
#include<queue>
#include<algorithm>
#include<iostream>
using namespace std;
bool byGreater(int a,int b)
{
    return a>b;
}
struct edge
{
    int from,to;
    int w;
};
vector<edge> adjList[100005];
int far[100005]; //Stores the minimum longest distance for each tree
int color[100005];
int d[2][100005];
queue<int> Q;
int bfs(int s,int op,int c)
{
    color[s]=c;
    d[op][s]=0;
    Q.push(s);
    int farthest_node;
    int maximum=0;
    while(Q.size()){
        int u=Q.front();Q.pop();
        for(edge e: adjList[u]){
            int v=e.to;
            if(color[v]!=c){
                color[v]=c;
                d[op][v]=d[op][u]+e.w;
                if(d[op][v]>maximum){
                    maximum=d[op][v];
                    farthest_node=v;
                }
                Q.push(v);
            }
        }
    }
    return farthest_node;
}
int getOptimumDistance(int s,int c)
{
    color[s]=c;
    int minimumD=1000000000;
    Q.push(s);
    while(Q.size()){
        int u=Q.front();Q.pop();
        if(max(d[0][u],d[1][u])<minimumD){
            minimumD=max(d[0][u],d[1][u]);
        }
        for(edge e: adjList[u]){
            int v=e.to;
            if(color[v]!=c){
                color[v]=c;
                Q.push(v);
            }
        }
    }
    return minimumD;
}
bool used[100005];
int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
    for(int i=0;i<M;i++){
        edge e={A[i],B[i],T[i]};
        adjList[e.from].push_back(e);
        swap(e.from,e.to);
        adjList[e.from].push_back(e);
    }
    int answer=0;
    int max_diameter=0;
    int c=1;
    int trees=0;
    for(int u=0;u<N;u++){
        if(color[u]!=0) continue;
        int a=bfs(u,1,c++);
        int b=bfs(a,0,c++);
        bfs(b,1,c++);
        max_diameter=max(max_diameter,d[1][a]);
        far[trees++]=getOptimumDistance(u,c++);
    }
    sort(far,far+trees,byGreater);
    //cout<<far[0]<<" "<<far[1]<<" "<<far[2]<<endl;
    if(trees==1){
        answer=max_diameter;
    }
    else if(trees==2){
        answer=max(max_diameter,far[0]+L+far[1]); //Path joining yourself with another tree
    }
    else{
        answer=max(max_diameter,
                   max(far[0]+L+far[1],far[1]+L+L+far[2])); //Path joining yourself with another tree
                   //and joining other two trees whose path passes for you
    }
    return answer;
}

Compilation message (stderr)

dreaming.cpp: In function 'int bfs(int, int, int)':
dreaming.cpp:43:12: warning: 'farthest_node' may be used uninitialized in this function [-Wmaybe-uninitialized]
     return farthest_node;
            ^~~~~~~~~~~~~

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