1475: 方格取数

 1 /**************************************************************
 2     Problem: 1475
 3     User: HansBug
 4     Language: Pascal
 5     Result: Accepted
 6     Time:304 ms
 7     Memory:612 kb
 8 ****************************************************************/
 9  
10 type
11     point=^node;
12     node=record
13                g,w:longint;
14                anti,next:point;
15     end;
16 var
17    i,j,k,l,m,n,s,t,flow:longint;
18    a,e:array[0..10000] of point;
19    b,c,d:array[0..10000] of longint;
20 function min(x,y:longint):longint;
21          begin
22               if x<y then min:=x else min:=y;
23          end;
24 procedure add(x,y,z:longint);
25           var p:point;
26           begin
27                new(p);p^.g:=y;p^.w:=z;p^.next:=a[x];a[x]:=p;
28                new(p);p^.g:=x;p^.w:=0;p^.next:=a[y];a[y]:=p;
29                a[x]^.anti:=a[y];a[y]^.anti:=a[x];
30           end;
31 function spfa:boolean;
32          var f,r,i:longint;p:point;
33           begin
34                for i:=s to t do c[i]:=maxlongint;
35                f:=1;r:=2;d[1]:=s;c[s]:=0;
36                while f<r do
37                      begin
38                           p:=a[d[f]];
39                           while p<>nil do
40                                 begin
41                                      if (p^.w<>0) and (c[p^.g]=maxlongint) then
42                                         begin
43                                              e[p^.g]:=p;
44                                              c[p^.g]:=c[d[f]]+1;
45                                              d[r]:=p^.g;inc(r);
46                                         end;
47                                      p:=p^.next;
48                                 end;
49                           inc(f);
50                      end;
51                exit(c[t]<>maxlongint);
52           end;
53 procedure deal;
54           begin
55                i:=t;l:=maxlongint;
56                while i<>s do
57                      begin
58                           l:=min(e[i]^.w,l);
59                           i:=e[i]^.anti^.g;
60                      end;
61                dec(flow,l);i:=t;
62                while i<>s do
63                      begin
64                           if e[i]^.w<>maxlongint then dec(e[i]^.w,l);
65                           if e[i]^.anti^.w<>maxlongint then inc(e[i]^.anti^.w,l);
66                           i:=e[i]^.anti^.g;
67                      end;
68           end;
69 begin
70      readln(n);flow:=0;s:=1;t:=n*n+2;
71      for i:=1 to n*n+2 do a[i]:=nil;
72      for i:=1 to n do
73          for j:=1 to n do
74              begin
75                   read(k);inc(flow,k);
76                   if odd(i+j) then add(1,(i-1)*n+j+1,k) else add((i-1)*n+j+1,n*n+2,k);
77                   if odd(i+j) then
78                      begin
79                           if i>1 then add((i-1)*n+j+1,(i-2)*n+j+1,maxlongint);
80                           if i<n then add((i-1)*n+j+1,(i)*n+j+1,maxlongint);
81                           if j>1 then add((i-1)*n+j+1,(i-1)*n+j,maxlongint);
82                           if j<n then add((i-1)*n+j+1,(i-1)*n+j+2,maxlongint);
83                      end;
84                   if j=n then readln;
85              end;
86      while spfa do deal;
87      writeln(flow);
88      readln;
89 end.