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Bessie is out in the field and wants to get back to the barn to get as much sleep as possible before Farmer John wakes her for the morning milking. Bessie needs her beauty sleep, so she wants to get back as quickly as possible.

Farmer John’s field has N (2 <= N <= 1000) landmarks in it, uniquely numbered 1…N. Landmark 1 is the barn; the apple tree grove in which Bessie stands all day is landmark N. Cows travel in the field using T (1 <= T <= 2000) bidirectional cow-trails of various lengths between the landmarks. Bessie is not confident of her navigation ability, so she always stays on a trail from its start to its end once she starts it. Given the trails between the landmarks, determine the minimum distance Bessie must walk to get back to the barn. It is guaranteed that some such route exists. Input Line 1: Two integers: T and N

Lines 2…T+1: Each line describes a trail as three space-separated integers. The first two integers are the landmarks between which the trail travels. The third integer is the length of the trail, range 1…100.

Output Line 1: A single integer, the minimum distance that Bessie must travel to get from landmark N to landmark 1. Sample Input 5 5 1 2 20 2 3 30 3 4 20 4 5 20 1 5 100 Sample Output 90 Hint INPUT DETAILS: There are five landmarks. OUTPUT DETAILS: Bessie can get home by following trails 4, 3, 2, and 1.

优先队列定义q就直接一个结构体就可以了，不要在写vector还是greater或者less了，写上去还麻烦，真的是伤心了。

#include 
   
    #include 
    
     #include 
     
      #include 
      
       using namespace std;const int inf = 0x3f3f3f3f;struct node{   	int d;	int pos;	};priority_queue
       
         q;bool operator < (node a, node b){   	return a.d > b.d;//权值小的边优先}int n , m;int e[2005][2005];int dis[2005];void dijkstra(int start){   	int book[2005];    memset(book, 0, sizeof(book));    	for (int i=1; i<=n; i++)    	if (i==start)	dis[i]=0;    	else	dis[i]=inf;    node t;    t.d=dis[start];    t.pos=start;    q.push(t);    while(!q.empty()){           		t = q.top();        q.pop();        int x = t.pos;        if(book[x]==1) 			continue;        book[x] = 1;        for(int j=1; j<=n; j++){               if(book[j]==0 && dis[j]>dis[x]+e[x][j]){                   dis[j]=dis[x]+e[x][j];                node tt;				tt.d=dis[j];                tt.pos=j;                q.push(tt);            }        }    }    cout<
        
         <
         
          w){ e[u][v]=w; e[v][u]=w; } } dijkstra(1); } return 0;}
         
        
       
      
     
    
   

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