骑士共存问题
题意略过，把棋盘上点交叉黑白染色，坏点为-1，则每个骑士在合理跳跃的前提下总会跳到一个不同颜色的点，我们把这两个点连边，
问题转化为最大独立子集问题，用匈牙利最大数据0.39水过，第9个点用cena暴栈，但是直接运行没有问题，囧
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1 program knight(input,output); 2 type 3 node = ^link; 4 link = record 5 goal : longint; 6 next : node; 7 end; 8 var 9 l : array[0..41000] of node; 10 map : array[0..201,0..201] of integer; 11 number : array[0..201,0..201] of longint; 12 lk : array[0..41000] of longint; 13 v : array[0..41000] of boolean; 14 n,m : longint; 15 procedure init; 16 var 17 i,j : longint; 18 sum : longint; 19 xx,yy : longint; 20 begin 21 readln(n,m); 22 for i:=1 to n*n do 23 l[i]:=nil; 24 map[1,1]:=0; 25 for i:=2 to n do 26 map[1,i]:=1-map[1,i-1]; 27 for i:=2 to n do 28 for j:=1 to n do 29 map[i,j]:=1-map[i-1,j]; 30 sum:=0; 31 for i:=1 to n do 32 for j:=1 to n do 33 begin 34 inc(sum); 35 number[i,j]:=sum; 36 end; 37 for i:=1 to m do 38 begin 39 readln(xx,yy); 40 map[xx,yy]:=-1; 41 end; 42 end; { init } 43 procedure add(x1,y1,x2,y2 : longint ); 44 var 45 tt : node; 46 begin 47 if (x1<1)or(x1>n)or(x2<1)or(x2>n) then 48 exit; 49 if (y1<1)or(y1>n)or(y2<1)or(y2>n) then 50 exit; 51 if (map[x1,y1]=-1)or(map[x2,y2]=-1) then 52 exit; 53 new(tt); 54 tt^.goal:=number[x2,y2]; 55 tt^.next:=l[number[x1,y1]]; 56 l[number[x1,y1]]:=tt; 57 end; { add } 58 procedure make_graph(); 59 var 60 i,j : longint; 61 begin 62 for i:=1 to n do 63 for j:=1 to n do 64 if map[i,j]=0 then 65 begin 66 add(i,j,i-2,j-1); 67 add(i,j,i-1,j-2); 68 add(i,j,i-2,j+1); 69 add(i,j,i-1,j+2); 70 add(i,j,i+1,j-2); 71 add(i,j,i+1,j+2); 72 add(i,j,i+2,j-1); 73 add(i,j,i+2,j+1); 74 end; 75 end; { make_graph } 76 function find(now :longint ):boolean; 77 var 78 t : node; 79 begin 80 t:=l[now]; 81 while t<>nil do 82 begin 83 if not v[t^.goal] then 84 begin 85 v[t^.goal]:=true; 86 if (lk[t^.goal]=0)or(find(lk[t^.goal])) then 87 begin 88 lk[t^.goal]:=now; 89 exit(true); 90 end; 91 end; 92 t:=t^.next; 93 end; 94 exit(false); 95 end; { find } 96 procedure main; 97 var 98 i,j : longint; 99 answer : longint; 100 begin 101 answer:=0; 102 for i:=1 to n do 103 for j:=1 to n do 104 if map[i,j]=0 then 105 begin 106 fillchar(v,sizeof(v),false); 107 if find(number[i,j]) then 108 inc(answer); 109 end; 110 writeln(n*n-m-answer); 111 end; { main } 112 begin 113 assign(input,'knight.in');reset(input); 114 assign(output,'knight.out');rewrite(output); 115 init; 116 make_graph; 117 main; 118 close(input); 119 close(output); 120 end.
