HDU 6386 Age of Moyu 2018 Multi-University Training Contest 7（最短路径dijkstra）

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
#include <map>
using namespace std;
 
const int MAXN = 200005;
const int INF = 0x3f3f3f3f;
 
int N,M;
struct edge{
	int to,next,kind;
}E[MAXN*2];//双向边，双倍空间 

int head[100005],tot;
int dis[100005];
inline void Add(int from, int to ,int c)
{
	E[tot].to=to;
	E[tot].next=head[from];
	E[tot].kind=c;
	head[from]=tot++;
	E[tot].to=from;
	E[tot].next=head[to];
	E[tot].kind=c;
	head[to]=tot++; 
}
inline void init()
{
	tot=0;
	memset(head,-1,sizeof(head));
}
struct D{
	int num,w,kind;
	D(){}
	D(int _num,int _w,int _kind)
	{
		num=_num,w=_w,kind=_kind;
	}
};
struct cmp
{
	bool operator ()(D a,D b)
	{
		return a.w>b.w;
	}
};
int BFS(int x)
{
	priority_queue<D,vector<D>,cmp> q;
	
	fill(dis,dis+N+1,INF);
	
	dis[x]=0;
	q.push(D(x,0,-1));
	D t;
	while(!q.empty())
	{
		t=q.top(); q.pop();
		
		if(t.w>dis[t.num])continue;//若要这个点比到达这个点的最短花费多，跳过
		if(t.num==N)return t.w;
		
		for(int i=head[t.num];~i;i=E[i].next)//i=-1停止
		{
			int l;
			if(E[i].kind==t.kind)l=dis[t.num];
			else l=dis[t.num]+1;
			if(l<dis[E[i].to])
			{
				dis[E[i].to]=l;
				q.push(D(E[i].to,l,E[i].kind));//这个最短路需要更新，入队
			 } 
		}
	}
	return -1;
}
int main(){
    
    while(scanf("%d %d",&N,&M) == 2){
        init();
        if(M == 0){
            printf("-1\n");
            continue;
        }
        int a,b,c;
        for(int i=1 ; i<=M ; ++i){
            scanf("%d %d %d",&a,&b,&c);
            Add(a,b,c);
        }
        printf("%d\n",BFS(1));
    }
    
    return 0;
}