洛谷 1608 路径统计

 1 #include<cstdio>
 2 #include<algorithm>
 3 #define N 2010
 4 #define rg register
 5 using namespace std;
 6 int n,m,tot=0,dis[N],pos[N],last[N],cnt[N],rec[N][N][11];
 7 struct edge{
 8     int to,pre,dis;
 9 }e[N*N];
10 struct heap{
11     int poi,dis;
12 }h[N];
13 inline int read(){
14     int k=0,f=1; char c=getchar(); 
15     while(c<‘0‘||c>‘9‘)c==‘-‘&&(f=-1),c=getchar();
16     while(‘0‘<=c&&c<=‘9‘)k=k*10+c-‘0‘,c=getchar();
17     return k*f;
18 }
19 inline void add(int x,int y,int z){
20     e[++tot]=(edge){y,last[x],z}; last[x]=tot;
21 }
22 inline void up(int x){
23     int fa;
24     while((fa=x>>1)&&h[fa].dis>h[x].dis){
25         swap(h[x],h[fa]); swap(pos[h[x].poi],pos[h[fa].poi]);
26         x=fa;
27     }
28 }
29 inline void down(int x){
30     int son;
31     while((son=x<<1)<=tot){
32         if(son<tot&&h[son+1].dis<h[son].dis) son++;
33         if(h[son].dis<h[x].dis){
34             swap(h[x],h[son]); swap(pos[h[x].poi],pos[h[son].poi]);
35             x=son;
36         }
37         else return;
38     }
39 }
40 inline void dijkstra(int x){
41     h[tot=pos[x]=cnt[x]=1]=(heap){x,dis[x]=0};
42     while(tot){
43         int now=h[1].poi; h[1]=h[tot--]; if(tot) down(1);
44         for(rg int i=last[now],to;i;i=e[i].pre)
45         if(dis[to=e[i].to]>=dis[now]+e[i].dis){
46             if(dis[to]==dis[now]+e[i].dis) cnt[to]+=cnt[now];
47             else{
48                 dis[to]=dis[now]+e[i].dis;
49                 cnt[to]=cnt[now];
50                 if(!pos[to]) h[pos[to]=++tot]=(heap){to,dis[to]};
51                 else h[pos[to]].dis=dis[to];
52                 up(pos[to]);
53             }
54         }
55     }
56 }
57 int main(){
58     n=read(); m=read();
59     for(rg int i=1;i<=n;i++) dis[i]=0X7f7f7f7f;
60     for(rg int i=1;i<=n;i++) cnt[i]=0;
61     for(rg int i=1;i<=m;i++){
62         int u=read(),v=read(),w=read();
63         if(!rec[u][v][w]) rec[u][v][w]++;
64         else continue;
65         add(u,v,w);
66     }
67     dijkstra(1);
68     if(cnt[n]) printf("%d %d\n",dis[n],cnt[n]);
69     else puts("No answer");
70     return 0;
71 }