Lennot

/*
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 */


/**
 *
 * @author alexey
 */
import java.util.*; 
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.NoSuchElementException;
import java.util.StringTokenizer;
public class Datatahti201641 {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        //  Scanner cfg=new Scanner(System.in);
        IO io =new IO();
        
        int city=io.nextInt();
        int connect=io.nextInt();
        long[][] cities = new long[city+1][2];
        int i=1;
       /* while(i<city+1){
            cities[i][0]=Long.MAX_VALUE;
            cities[i][1]=Long.MAX_VALUE;
            i++;
        }*/
        cities[1][0]=0;
        cities[1][1]=0;
      ArrayList<ArrayList<int[]>> connections= new  ArrayList<ArrayList<int[]>>();
      connections.add(new ArrayList());
        for (int j = 0; j < city; j++) {
            connections.add(new ArrayList<int[]>());
        }
        
        for (int j = 0; j < connect; j++) {
            int a=io.nextInt();
            int b=io.nextInt();
            int c=io.nextInt();
            int[] d =new int[2];
            d[0]=b;
            d[1]=c;
            connections.get(a).add(d);
        }
     
        Set check = new HashSet();
        Set check2 = new HashSet();
        
        check.add(1);
        while(true){
            for(Object b:check){
                int a=(Integer) b;
                for(int[] k:connections.get(a)){
                    long x=cities[k[0]][0];
                    long y=k[1]+cities[a][1];
                    
                    if(x>y||(cities[k[0]][0]==0)){
                        check2.add(k[0]);
                        cities[k[0]][0]=y;
                    }
                }
            }
            check.clear();
            if(check2.isEmpty()){
                break;
            }
          
            
            for(Object c:check2){
                int a= (Integer) c;
                for(int[] k:connections.get(a)){
                    long x=cities[k[0]][1];
                    long y=cities[a][0];
                    if(x>y||cities[k[0]][1]==0){
                        check.add(k[0]);
                        cities[k[0]][1]=y;
                    }
                }
            }
            
        if(check.isEmpty()){
                break;
            }
            check2.clear();
        }
        if(cities[city][0]==0){
            io.println(cities[city][1]);
        }else if(cities[city][1]==0){
            io.println(cities[city][0]);
        }else{
          io.println(Math.min(cities[city][0], cities[city][1]));  
        }
        
       io.close();
    }
    
static class IO extends PrintWriter {
	private BufferedReader r;
	private StringTokenizer s;
	
	public IO() {
		super(new BufferedOutputStream(System.out));
		r = new BufferedReader(new InputStreamReader(System.in));
	}
	
	public String nextLine() {
		String s = null;
		try {
			s = r.readLine();
		} catch (Exception e) {}
		if(s == null) throw new NoSuchElementException();
		return s;
	}
	
	public String next() {
		while (s == null || !s.hasMoreElements()) {
			s = new StringTokenizer(nextLine());
		}
		return s.nextToken();
	}
        public int nextInt() {
		return Integer.parseInt(next());
	}
}
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 13

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 15

Group: 3

Verdict: ACCEPTED

Test 16

Group: 3

Verdict: ACCEPTED

Test 17

Group: 3

Verdict: ACCEPTED