java 代码

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

class Main{
    static int n = 0, m = 0, k = 0;
    static int N = 10010;
    static int[][] edges = new int[N][3];
    static int[] dist = new int[510];
    static int[] backup = new int[510];
    static int bellmanFord(){
        Arrays.fill(dist, 0x3f3f3f3f);
        dist[1] = 0;
        for(int i = 0; i < k; ++i){
            backup = Arrays.copyOf(dist, N);
            for(int j = 1; j <= m; ++j){
                int a = edges[j][0], b = edges[j][1], w = edges[j][2];
                dist[b] = Math.min(dist[b], backup[a] + w);
            }
        }
        if(dist[n] >= 0x3f3f3f3f / 2)return -1;
        return dist[n];

    }

    public static void main(String[] args)throws Exception{
        BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));
        String[] params = buf.readLine().split(" ");
        n = Integer.valueOf(params[0]);
        m = Integer.valueOf(params[1]);
        k = Integer.valueOf(params[2]);
        for(int i = 1; i <= m; ++i){
            String[] info = buf.readLine().split(" ");
            edges[i][0] = Integer.valueOf(info[0]);//入
            edges[i][1] = Integer.valueOf(info[1]);//出
            edges[i][2] = Integer.valueOf(info[2]);//权值
        }
        int cond = bellmanFord();
        if(cond != -1){
            System.out.print(cond);
        }else{
            System.out.print("impossible");
        }

    }
}