2016huasacm暑假集训训练三 C

题目链接：https://vjudge.net/contest/123674#problem/C

N题目大意是有n个点，然后给出从a点到b点的距离，a和b是互相可以抵达的，则是无向图，问从1到n的最短距离

解题思路：只是一道简单的最短路问题，按照最短路模板就能AC,但这题还有有个主意点，就是重边问题，但我用的是spfa算法，就不需要考虑这个问题，如果是dijkstra算法就要考虑这个问题；

ac代码：

import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Scanner;
public class Main {
    static int n, m;
    static int[][] map = new int[1001][1001];
    static int[] dis = new int[1001];
    static boolean[] vis = new boolean[1001];
    static final int Inf = 0x3f3f3f3f;
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int u, v, w;
        while (sc.hasNext()) {
            m = sc.nextInt();n = sc.nextInt();
            for (int i = 1; i <= n; i++) {
                for (int j = i; j <= n; j++) {    
                    map[i][j] = Inf;
                    map[j][i] = Inf;
                }
            }
            for (int i = 0; i < m; i++) {  //建图
                u = sc.nextInt();
                v = sc.nextInt();
                w = sc.nextInt();
                if (map[u][v] > w) {  //spfa算法，已经考虑了重边问题，所以不需要再考虑
                    map[v][u] = w;
                    map[u][v] = w;
                }
            }
            spfa(1);
                System.out.println(dis[n]);  //输出1~n的最短距离
        }
        sc.close();
    }
private static void spfa(int s) {

        for (int i = 1; i <= n; i++) {
            vis[i] = false;
            dis[i] = Inf;
        }
        dis[s] = 0;
        vis[s] = true;
        Comparator<Integer> cmp = new Comparator<Integer>() {

            public int compare(Integer o1, Integer o2) {
                int i = (int) o1;
                int j = (int) 02;
                if (dis[i] > dis[j]) {
                    return 1;
                } else if (dis[i] == dis[j]) {
                    return 0;
                } else {
                    return -1;
                }
            }
        };
        Queue<Integer> q = new PriorityQueue<Integer>(1001, cmp);
        q.clear();
        q.offer(s);
        while (!q.isEmpty()) {
            int head = q.poll();
            vis[head] = false;
            for (int i = 1; i <= n; i++) {
                int temp = dis[head] + map[head][i];
                if (temp < dis[i]) {
                    dis[i] = temp;
                    if (!vis[i]) {
                        q.offer(i);
                        vis[i] = true;