P1179: [Apio2009]Atm
缩点+spfa最短路，因为最终不可能有环，所以直接spfa。
1 const maxe=1000001;
2 type
3 node=record
4 f,t:longint;
5 end;
6 var n,m,s,i,j,ans,cnt,num,u,x,dgr:longint;
7 h,he,dfn,low,q,d,v,va,bl:array[0..maxe] of longint;
8 b,bi:array[0..maxe] of node;
9 f:array[0..maxe*20] of longint;
10 p:array[0..maxe] of boolean;
11 function min(a,b:longint):longint;
12 begin
13 if a>b then exit(b) else exit(a);
14 end;
15 procedure insert(u,v:longint);
16 begin
17 with bi[i] do
18 begin
19 f:=he[u];
20 t:=v;
21 end;
22 he[u]:=i;
23 end;
24 procedure reinsert(u,v:longint);
25 begin
26 inc(cnt);
27 with b[cnt] do
28 begin
29 f:=h[u];
30 t:=v;
31 end;
32 h[u]:=cnt;
33 end;
34 procedure readd;
35 var i,e,v:longint;
36 begin
37 cnt:=0;
38 for i:=1 to n do
39 begin
40 e:=he[i];
41 while e<>0 do
42 begin
43 v:=bi[e].t;
44 if bl[i]<>bl[v] then reinsert(bl[i],bl[v]);
45 e:=bi[e].f;
46 end;
47 end;
48 end;
49 procedure tarjan(x:longint);
50 var e,t,j:longint;
51 begin
52 inc(dgr); inc(num);
53 p[x]:=true; f[num]:=x; dfn[x]:=dgr; low[x]:=dgr;
54 e:=he[x];
55 while e<>0 do
56 begin
57 t:=bi[e].t;
58 if dfn[t]=0 then
59 begin
60 tarjan(t);
61 if low[x]>low[t] then low[x]:=low[t];
62 end
63 else if (p[t]) and (dfn[t]<low[x]) then low[x]:=dfn[t];
64 e:=bi[e].f;
65 end;
66 if dfn[x]=low[x] then
67 begin
68 j:=0; inc(cnt);
69 while j<>x do
70 begin
71 j:=f[num];
72 dec(num);
73 p[j]:=false;
74 bl[j]:=cnt;
75 //writeln(j,' ',cnt);
76 inc(v[cnt],va[j]);
77 end;
78 end;
79 end;
80 procedure spfa;
81 var e,t,now,l,r:longint;
82 begin
83 fillchar(p,sizeof(p),true);
84 fillchar(d,sizeof(d),0);
85 l:=1; r:=1; f[1]:=bl[s]; p[bl[s]]:=false; d[bl[s]]:=v[bl[s]]; //writeln(v[bl[s]]);
86 while l<=r do
87 begin
88 now:=f[l];
89 e:=h[now];
90 while e<>0 do
91 begin
92 t:=b[e].t;
93 //if t=1 then writeln('x',now,' ',v[t]);
94 if d[t]<d[now]+v[t] then
95 begin
96 d[t]:=d[now]+v[t];
97 if p[t] then
98 begin
99 p[t]:=false;
100 inc(r);
101 f[r]:=t;
102 end;
103 end;
104 e:=b[e].f;
105 end;
106 inc(l);
107 p[now]:=true;
108 end;
109 end;
110 begin
111 readln(n,m);
112 for i:=1 to m do
113 begin
114 readln(u,x);
115 insert(u,x);
116 end;
117 for i:=1 to n do readln(va[i]);
118 fillchar(p,sizeof(p),false);
119 for i:=1 to n do if dfn[i]=0 then tarjan(i);
120 readln(s,m);
121 readd;
122 //for i:=1 to 4 do writeln(v[i]);
123 spfa;
124 for i:=1 to m do
125 begin
126 read(u);
127 if d[bl[u]]>ans then ans:=d[bl[u]];
128 end;
129 writeln(ans);
130 end.
(转载请注明出处：http://www.cnblogs.com/Kalenda/)
