• pku2226 Muddy Fields


    最小覆盖问题,跟3041差不多,只不过有了不能覆盖点的限制,首先横竖染色,那么每个水坑要么没横着的覆盖,要么被竖着的覆盖,用染出色的该点木板颜色连边,求最大匹配即可。

    View Code
      1 program pku2226(input,output);
    2 var
    3 map : array[0..51,0..51] of char;
    4 x,y : array[0..51,0..51] of longint;
    5 f : array[0..2500,0..2500] of boolean;
    6 v : array[0..2500] of boolean;
    7 lk : array[0..2500] of longint;
    8 n,m : longint;
    9 ll,rr : longint;
    10 procedure init;
    11 var
    12 i,j : longint;
    13 begin
    14 readln(n,m);
    15 for i:=1 to n do
    16 begin
    17 for j:=1 to m do
    18 read(map[i,j]);
    19 readln;
    20 end;
    21 fillchar(x,sizeof(x),255);
    22 fillchar(y,sizeof(y),255);
    23 end; { init }
    24 procedure make_graph();
    25 var
    26 i,j : longint;
    27 tot : longint;
    28 begin
    29 tot:=0;
    30 for i:=1 to n do
    31 for j:=1 to m do
    32 begin
    33 if map[i,j]='.' then
    34 continue
    35 else
    36 begin
    37 if x[i,j-1]<>-1 then
    38 x[i,j]:=x[i,j-1]
    39 else
    40 begin
    41 inc(tot);
    42 x[i,j]:=tot;
    43 end;
    44 end;
    45 end;
    46 ll:=tot+1;
    47
    48 for i:=1 to m do
    49 for j:=1 to n do
    50 begin
    51 if map[j,i]='.' then
    52 continue
    53 else
    54 begin
    55 if y[j-1,i]<>-1 then
    56 y[j,i]:=y[j-1,i]
    57 else
    58 begin
    59 inc(tot);
    60 y[j,i]:=tot;
    61 end;
    62 end;
    63 end;
    64 rr:=tot;
    65
    66 fillchar(f,sizeof(f),false);
    67 for i:=1 to n do
    68 for j:=1 to m do
    69 if map[i,j]='*' then
    70 f[x[i,j],y[i,j]]:=true;
    71 end; { make_graph }
    72 function find(now :longint ):boolean;
    73 var
    74 i : longint;
    75 begin
    76 for i:=ll to rr do
    77 if (not v[i])and(f[now,i]) then
    78 begin
    79 v[i]:=true;
    80 if (lk[i]=0)or(find(lk[i])) then
    81 begin
    82 lk[i]:=now;
    83 exit(true);
    84 end;
    85 end;
    86 exit(false);
    87 end; { find }
    88 function main:longint;
    89 var
    90 i : longint;
    91 begin
    92 main:=0;
    93 fillchar(lk,sizeof(lk),0);
    94 for i:=1 to ll-1 do
    95 begin
    96 fillchar(v,sizeof(v),false);
    97 if find(i) then
    98 inc(main);
    99 end;
    100 end; { main }
    101 begin
    102 while not eof do
    103 begin
    104 init;
    105 make_graph;
    106 writeln(main);
    107 end;
    108 end.



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  • 原文地址:https://www.cnblogs.com/neverforget/p/2379448.html
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