P2763: [JLOI2011]飞行路线

然而WA了呀，这道分层图，也是不明白为什么WA了=-=

 1 const maxe=1400001; maxn=100000000001; points=300001;
 2 type
 3   node=record
 4     f,t,l:longint;
 5   end;
 6 var n,m,k,i,j,u,v,x,s,t,num:longint;
 7 b:array[0..maxe] of node;
 8 ans:int64;
 9 f:array[0..50000000] of longint;
10 p:array[0..points] of boolean;
11 head:array[0..points] of longint;
12 d:array[0..points] of int64;
13 procedure insert(u,v,x:longint);
14 begin
15   inc(num);
16   b[num].f:=head[u];
17   b[num].t:=v;
18   b[num].l:=x;
19   head[u]:=num;
20 end;
21 procedure spfa;
22 var now,nowe,l,r,v:longint;
23 begin
24   for l:=1 to points do d[l]:=maxn;
25   fillchar(p,sizeof(p),true);
26   l:=1; r:=1; f[1]:=s; d[s]:=0; p[s]:=false; ans:=maxn; //writeln(ans);
27   while l<=r do
28     begin
29       now:=f[l];
30       nowe:=head[now];
31       while nowe<>0 do
32         begin
33           v:=b[nowe].t;
34           if d[now]+b[nowe].l<d[v] then
35             begin
36               d[v]:=d[now]+b[nowe].l;
37               if p[v] then
38                 begin
39                   p[v]:=false;
40                   inc(r);
41                   f[r]:=v;
42                 end;
43               //if ((v mod k)=t) and (d[v]<ans) then ans:=d[v];
44             end;
45           nowe:=b[nowe].f;
46         end;
47       inc(l);
48       p[now]:=true;
49     end;
50   for l:=0 to k do
51     if ans>d[l*n+t] then ans:=d[l*n+t];
52 end;
53 begin
54   readln(n,m,k);
55   readln(s,t);
56   inc(s); inc(t);
57   for i:=1 to m do
58     begin
59       readln(u,v,x);
60       inc(u); inc(v);
61       for j:=0 to k do
62         begin
63           insert(u+j*n,v+j*n,x);
64           insert(v+j*n,u+j*n,x);
65           if j<>k then
66             begin
67               insert(u+j*n,v+(j+1)*n,0);
68               insert(v+j*n,u+(j+1)*n,0);
69             end;
70         end;
71     end;
72   spfa;
73   if ans=maxn then writeln(0)
74     else writeln(ans);
75 end.

暂且先不管为什么WA吧，首先这是个分层图原图既然是一层的。我们把它拆成k+1层。每一条边既能连本层，也能连到下一层。然后直接裸上Dijikstra即可，而spfa大概也是可以的吧。

而这是正解

 1 #include <queue>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <iostream>
 5 #include <algorithm>
 6 #define N 1200100
 7 using namespace std;
 8 int n,m,k;
 9 int st,ed,cnt;
10 int head[N];
11 int dis[N];
12 int v[N];
13 struct node
14 {
15     int from,to,val,next;
16 }edge[N<<1];
17 struct element
18 {
19     int val,no;
20 };
21 bool operator < (element a,element b)
22 {
23     if(a.val==b.val)return a.no<b.no;
24     return a.val>b.val;
25 }
26 priority_queue<element>q;
27 void dijikstra(int s,int e)
28 {
29     memset(dis,0x3f,sizeof(dis));
30     element fir;
31     fir.val=0,fir.no=s;
32     dis[s]=0;
33     q.push(fir);
34     while(!q.empty())
35     {
36         element u=q.top();
37         q.pop();
38         if(v[u.no])continue;
39         v[u.no]=1;
40         for(int i=head[u.no];i!=-1;i=edge[i].next)
41         {
42             int to=edge[i].to;
43             if(dis[u.no]+edge[i].val<dis[to])
44             {
45                 dis[to]=dis[u.no]+edge[i].val;
46                 element pus;
47                 pus.no=to,pus.val=dis[to];
48                 q.push(pus);
49             }
50         }
51     }
52     int ans=0x3f3f3f3f;
53     for(int i=0;i<=k;i++)
54     {
55         ans=min(ans,dis[e+i*n]);
56     }
57     printf("%d\n",ans);
58 }
59 void init()
60 {
61     memset(head,-1,sizeof(head));
62     cnt=1;
63 }
64 void edgeadd(int from,int to,int val)
65 {
66     edge[cnt].from=from;
67     edge[cnt].to=to;
68     edge[cnt].val=val;
69     edge[cnt].next=head[from];
70     head[from]=cnt++;
71 }
72
73 int main()
74 {
75     init();
76     scanf("%d%d%d",&n,&m,&k);
77     scanf("%d%d",&st,&ed);
78     st++,ed++;
79     for(int i=1;i<=m;i++)
80     {
81         int x,y,z;
82         scanf("%d%d%d",&x,&y,&z);
83         x++,y++;
84         for(int i=0;i<=k;i++)
85         {
86             edgeadd(x+i*n,y+i*n,z);
87             edgeadd(y+i*n,x+i*n,z);
88             if(i!=k)
89             {
90                 edgeadd(x+i*n,y+(i+1)*n,0);
91                 edgeadd(y+i*n,x+(i+1)*n,0);
92             }
93         }
94     }
95     dijikstra(st,ed);
96 }