java 代码

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

class Main{
    static int n = 0, m = 0, N = 1000010;
    static PriorityQueue<int[]> q = new PriorityQueue<>((a,b)->{return a[1] - b[1];});//堆
    static int[] dist = new int[N];//距离数组
    static boolean[] f = new boolean[N];//标记数组
    static int[] h = new int[N], ne = new int[N], e = new int[N], w = new int[N];//邻接表
    static int idx = 1;
    static int Dijkstra(){//类似广搜的过程
        Arrays.fill(dist, 0x3f3f3f3f);
        dist[1] = 0;//初始化第一个点到自身的距离
        q.offer(new int[]{1, 0});
        while(q.size() != 0){
            int[] a = q.poll();
            int t = a[0], distance = a[1];
            if(f[t])continue;
            f[t] = true;
            for(int i = h[t]; i != -1; i = ne[i]){
               int j = e[i];
               if(dist[j] > distance + w[i]){
                   dist[j] = distance + w[i];
                   q.offer(new int[]{j, dist[j]});
               }
            }
        }
        if(dist[n] != 0x3f3f3f3f)return dist[n];
        return -1;
    }
    static void add(int a, int b, int c){
        e[idx] = b; w[idx] = c;ne[idx] = h[a]; h[a] = idx++;
    }
    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]);
        Arrays.fill(h, -1);
        for(int i = 1; i <= m; ++i){
            String[] info = buf.readLine().split(" ");
            int a = Integer.valueOf(info[0]);
            int b = Integer.valueOf(info[1]);
            int c = Integer.valueOf(info[2]);
            add(a, b, c);
        }
        System.out.print(Dijkstra());

    }
}