AHOI2009最小割

  1  const inf=maxlongint;
  2 type node=record
  3      from,go,next,v:longint;
  4      end;
  5 var  tot,i,j,n,m,maxflow,l,r,s,t,x,y,z,ti,top,cnt,xx,yy:longint;
  6      h,head,q,cur,low,dfn,sta,scc:array[0..10000] of longint;
  7      e:array[0..200000] of node;
  8      function min(x,y:longint):longint;
  9       begin
 10       if x<y then exit(x) else exit(y);
 11       end;
 12 procedure ins(x,y,z:longint);
 13  begin
 14  inc(tot);
 15  e[tot].from:=x;e[tot].go:=y;e[tot].v:=z;e[tot].next:=head[x];head[x]:=tot;
 16  end;
 17 procedure insert(x,y,z:longint);
 18  begin
 19  ins(x,y,z);ins(y,x,0);
 20  end;
 21 function bfs:boolean;
 22  var i,x,y:longint;
 23  begin
 24  fillchar(h,sizeof(h),0);
 25  l:=0;r:=1;q[1]:=s;h[s]:=1;
 26  while l<r do
 27   begin
 28   inc(l);
 29   x:=q[l];
 30   i:=head[x];
 31   while i<>0 do
 32    begin
 33    y:=e[i].go;
 34    if (e[i].v<>0) and (h[y]=0) then
 35     begin
 36      h[y]:=h[x]+1;
 37      inc(r);q[r]:=y;
 38     end;
 39    i:=e[i].next;
 40    end;
 41   end;
 42  exit (h[t]<>0);
 43  end;
 44 function dfs(x,f:longint):longint;
 45  var i,y,used,tmp:longint;
 46  begin
 47  if x=t then exit(f);
 48  used:=0;
 49  i:=cur[x];
 50  while i<>0 do
 51   begin
 52   y:=e[i].go;
 53   if (h[y]=h[x]+1) and (e[i].v<>0) then
 54    begin
 55    tmp:=dfs(y,min(e[i].v,f-used));
 56    dec(e[i].v,tmp);if e[i].v<>0 then cur[x]:=i;
 57    inc(e[i xor 1].v,tmp);
 58    inc(used,tmp);
 59    if used=f then exit(f);
 60    end;
 61   i:=e[i].next;
 62   end;
 63  if used=0 then h[x]:=-1;
 64  exit(used);
 65  end;
 66 procedure dinic;
 67  begin
 68  while bfs do
 69   begin
 70   for i:=1 to n do cur[i]:=head[i];
 71   inc(maxflow,dfs(s,inf));
 72   end;
 73  end;
 74 procedure init;
 75  begin
 76  tot:=1;
 77  readln(n,m,s,t);
 78      for i:=1 to m do
 79       begin
 80         readln(x,y,z);
 81         insert(x,y,z);
 82       end;
 83  end;
 84 procedure dfs(x:longint);
 85  var i,y,z:longint;
 86  begin
 87  inc(ti);dfn[x]:=ti;low[x]:=ti;inc(top);sta[top]:=x;
 88  i:=head[x];
 89  while i<>0 do
 90   begin
 91    y:=e[i].go;
 92    if e[i].v<>0 then
 93     begin
 94      if dfn[y]=0 then
 95       begin
 96        dfs(y);
 97       low[x]:=min(low[x],low[y]);
 98       end
 99     else if scc[y]=0 then low[x]:=min(low[x],dfn[y]);
100     end;
101   i:=e[i].next;
102   end;
103  if low[x]=dfn[x] then
104   begin
105   inc(cnt);
106   while true do
107    begin
108    z:=sta[top];dec(top);
109    scc[z]:=cnt;
110    if z=x then break;
111    end;
112   end;
113  end;
114 procedure tarjan;
115  begin
116  ti:=0;cnt:=0;ti:=0;
117  fillchar(dfn,sizeof(dfn),0);
118  for i:=1 to n do if dfn[i]=0 then dfs(i);
119  end;
120 procedure main;
121  begin
122   dinic;
123   tarjan;
124   x:=scc[s];y:=scc[t];
125   for i:=2 to tot do
126    if (i and 1=0) then
127      begin
128      if e[i].v<>0 then begin writeln(‘0 0‘);continue;end;
129      xx:=scc[e[i].from];yy:=scc[e[i].go];
130      if xx<>yy then write(‘1‘) else write(‘0‘);write(‘ ‘);
131      if (xx=x) and (yy=y) then write(‘1‘) else write(‘0‘);
132      writeln;
133      end;
134  end;
135 begin
136  assign(input,‘input.txt‘);assign(output,‘output.txt‘);
137  reset(input);rewrite(output);
138  init;
139  main;
140  close(input);close(output);
141 end.