Aizu Online Judge 0212 Highway Express Bus

■0212 Highway Express Bus

拡張Dijkstra．ノードを(今いる町, 残りチケット枚数)とする．後は次状態に遷移する際に，チケットを使った場合と使わなかった場合で更新．

import java.util.*;
import java.lang.*;
import java.math.*;
import java.io.*;

import static java.lang.Math.*;
import static java.util.Arrays.*;

public class Main{

 Scanner sc=new Scanner(System.in);

 int INF=1<<28;
 double EPS=1e-9;

 int c, n, m, s, g;
 LinkedList<E>[] es;

 @SuppressWarnings("unchecked")
 void run(){
  for(;;){
   c=sc.nextInt();
   n=sc.nextInt();
   m=sc.nextInt();
   s=sc.nextInt()-1;
   g=sc.nextInt()-1;
   if((c|n|m|(s+1)|(g+1))==0){
    break;
   }
   es=new LinkedList[n];
   for(int i=0; i<n; i++){
    es[i]=new LinkedList<E>();
   }
   for(int i=0; i<m; i++){
    int u=sc.nextInt()-1;
    int v=sc.nextInt()-1;
    int w=sc.nextInt()/10;
    es[u].add(new E(v, w));
    es[v].add(new E(u, w));
   }
   solve();
  }
 }

 void solve(){
  int[][] d=new int[n][c+1];
  PriorityQueue<P> que=new PriorityQueue<P>();

  for(int i=0; i<n; i++){
   Arrays.fill(d[i], INF);
  }
  d[s][c]=0;
  que.offer(new P(s, c, 0));
  for(; !que.isEmpty();){
   P p=que.poll();
   if(d[p.v][p.c]<p.d){
    continue;
   }
   for(E e : es[p.v]){
    if(d[e.to][p.c]>d[p.v][p.c]+e.cost){
     d[e.to][p.c]=d[p.v][p.c]+e.cost;
     que.offer(new P(e.to, p.c, d[e.to][p.c]));
    }
    if(p.c>0&&d[e.to][p.c-1]>d[p.v][p.c]+e.cost/2){
     d[e.to][p.c-1]=d[p.v][p.c]+e.cost/2;
     que.offer(new P(e.to, p.c-1, d[e.to][p.c-1]));
    }
   }
  }
  int min=INF;
  for(int i=0; i<=c; i++){
   min=min(min, d[g][i]);
  }
  min*=10;
  println(""+min);
 }

 class E{
  int to, cost;

  E(int to, int cost){
   this.to=to;
   this.cost=cost;
  }
 }

 class P implements Comparable<P>{
  int v, c, d;

  P(int v, int c, int d){
   this.v=v;
   this.c=c;
   this.d=d;
  }

  @Override
  public int compareTo(P p){
   return d-p.d;
  }
 }

 void debug(Object... os){
  System.err.println(Arrays.deepToString(os));
 }

 void print(String s){
  System.out.print(s);
 }

 void println(String s){
  System.out.println(s);
 }

 public static void main(String[] args){
  // System.setOut(new PrintStream(new BufferedOutputStream(System.out)));
  new Main().run();
 }
}