[code]poj3349 Snowflake Snow Snowflakes

哈希+挂链。可以用next数组挂链。

 const p=;
 type
   arr=array[..]of longint;
 var
   a,b:Array[..]of arr;
   next:Array[..]of longint;
   i,j,n,has,tot:longint;

 function hash(x:longint):longint;
   var i:longint;
   begin
   hash:=;
   for i:= to  do
     hash:=(hash*+a[x,i]*) mod p;
   inc(hash);
   end;
 function equa(a,b:arr):boolean;
   var i:longint;
   begin
   for i:= to  do
     if a[i]<>b[i] then exit(false);
   exit(true);
   end ;
 procedure sort(var a:arr);
   var i,j,t:longint;
   begin
   for i:= to  do
     for j:=i to  do
       if a[j]>a[i] then
         begin t:=a[j];a[j]:=a[i];a[i]:=t;end;
   end;

 begin
   readln(n);
   tot:=p+;
   for i:= to n do
     begin
     for j:= to  do
       read(a[i,j]);
     sort(a[i]);
     has:=hash(i);
     while (has<>)and(not equa(b[has],b[])) do
       begin
       if equa(b[has],a[i]) then
         begin
         writeln('Twin snowflakes found.');
         halt;
         end;
       has:=next[has];
       end;
     next[has]:=tot+; inc(tot);
     b[has]:=a[i];
     end;
   writeln('No two snowflakes are alike.');
   end.