2016huasacm暑假集训训练三 C - Til the Cows Come Home

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