CH Round #17 舞动的夜晚

  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,ans,num,cnt,ti,top:longint;
  6      h,head,q,cur,a,dfn,low,sta,scc,x,y:array[0..500000] of longint;
  7      e:array[0..5000000] of node;
  8      b:array[0..500000] of boolean;
  9      function min(x,y:longint):longint;
 10       begin
 11       if x<y then exit(x) else exit(y);
 12       end;
 13 procedure ins(x,y,z:longint);
 14  begin
 15  inc(tot);
 16  e[tot].from:=x;e[tot].go:=y;e[tot].v:=z;e[tot].next:=head[x];head[x]:=tot;
 17  end;
 18 procedure insert(x,y,z:longint);
 19  begin
 20  ins(x,y,z);ins(y,x,0);
 21  end;
 22 function bfs:boolean;
 23  var i,x,y:longint;
 24  begin
 25  fillchar(h,sizeof(h),0);
 26  l:=0;r:=1;q[1]:=s;h[s]:=1;
 27  while l<r do
 28   begin
 29   inc(l);
 30   x:=q[l];
 31   i:=head[x];
 32   while i<>0 do
 33    begin
 34    y:=e[i].go;
 35    if (e[i].v<>0) and (h[y]=0) then
 36     begin
 37      h[y]:=h[x]+1;
 38      inc(r);q[r]:=y;
 39     end;
 40    i:=e[i].next;
 41    end;
 42   end;
 43  exit (h[t]<>0);
 44  end;
 45 function dfs(x,f:longint):longint;
 46  var i,y,used,tmp:longint;
 47  begin
 48  if x=t then exit(f);
 49  used:=0;
 50  i:=cur[x];
 51  while i<>0 do
 52   begin
 53   y:=e[i].go;
 54   if (h[y]=h[x]+1) and (e[i].v<>0) then
 55    begin
 56    tmp:=dfs(y,min(e[i].v,f-used));
 57    dec(e[i].v,tmp);if e[i].v<>0 then cur[x]:=i;
 58    inc(e[i xor 1].v,tmp);
 59    inc(used,tmp);
 60    if used=f then exit(f);
 61    end;
 62   i:=e[i].next;
 63   end;
 64  if used=0 then h[x]:=-1;
 65  exit(used);
 66  end;
 67 procedure dinic;
 68  begin
 69  while bfs do
 70   begin
 71   for i:=s to t do cur[i]:=head[i];
 72   inc(maxflow,dfs(s,inf));
 73   end;
 74  end;
 75 procedure dfs(x:longint);
 76  var i,y,z:longint;
 77  begin
 78  inc(ti);dfn[x]:=ti;low[x]:=ti;inc(top);sta[top]:=x;
 79  i:=head[x];
 80  while i<>0 do
 81   begin
 82    y:=e[i].go;
 83    if e[i].v<>0 then
 84      begin
 85       if dfn[y]=0 then
 86        begin
 87        dfs(y);
 88        low[x]:=min(low[x],low[y]);
 89        end
 90       else if scc[y]=0 then low[x]:=min(low[x],dfn[y]);
 91      end;
 92    i:=e[i].next;
 93    end;
 94  if low[x]=dfn[x] then
 95   begin
 96   inc(cnt);
 97   while true do
 98    begin
 99    z:=sta[top];dec(top);
100    scc[z]:=cnt;
101    if z=x then break;
102    end;
103   end;
104  end;
105 procedure tarjan;
106  begin
107  ti:=0;cnt:=0;ti:=0;
108  fillchar(dfn,sizeof(dfn),0);
109  for i:=s to t do if dfn[i]=0 then dfs(i);
110  end;
111 procedure init;
112  begin
113  tot:=1;
114  readln(n,m,num);
115  s:=0;t:=n+m+1;
116  for i:=1 to n do insert(s,i,1);
117  for i:=1 to num do
118   begin
119   readln(x[i],y[i]);inc(y[i],n);
120   a[i]:=tot+1;insert(x[i],y[i],1);
121   end;
122  for i:=n+1 to n+m do insert(i,t,1);
123  end;
124 procedure main;
125  begin
126  maxflow:=0;
127  dinic;
128  tarjan;
129  ans:=0;
130  for i:=1 to num do
131   begin
132   if (e[a[i]].v<>0) and (scc[x[i]]<>scc[y[i]]) then
133     begin
134     b[i]:=true;inc(ans);
135     end;
136   end;
137  writeln(ans);
138  if ans=0 then writeln else for i:=1 to num do if b[i] then write(i,‘ ‘);
139  end;
140 
141 begin
142  assign(input,‘input.txt‘);assign(output,‘output.txt‘);
143  reset(input);rewrite(output);
144  init;
145  main;
146  close(input);close(output);
147 end.