[POJ2503 Babelfish]

[题目来源]：POJ2503

[关键字]：hash

[题目大意]：给出一个字典，和一些待查询的单词，要求查处所有单词，没有则输出‘eh’。

//===========================================================================================================

[分析]：可以将整个字典进行字符串hash，然后查找。

[代码]：（题目代码+各种字符串Hash）

POJ2503

 1 program Project1;
 2 type
 3   rec = record
 4     o, t: string[11];
 5   end;
 6 var
 7   num: array[0..20000] of longint;
 8   h: array[0..20000,0..10] of rec;
 9   
10 function hash(s: string):longint;
11 var
12   seek, i: longint;
13 begin
14   seek := 31;
15   hash := 0;
16   for i := 1 to length(s) do
17     hash := (hash*seek+ord(s[i])) and $FFFFFFFF;
18   hash := hash and $7FFFFFFF;
19 end;
20 
21 procedure init;
22 var
23   k, i: longint;
24   s, s1: string;
25   f: boolean;
26 begin
27   readln(s);
28   while s <> '' do
29     begin
30       s1 := copy(s,1,pos(' ',s)-1);
31       delete(s,1,pos(' ',s));
32       k := hash(s) mod 15889;
33       //writeln(k);
34       inc(num[k]);
35       h[k,num[k]].o := s;
36       h[k,num[k]].t := s1;
37       readln(s);
38     end;
39 
40   while not seekeof do
41     begin
42       readln(s);
43       k := hash(s) mod 15889;
44       f := false;
45       for i := 1 to num[k] do
46         if h[k,i].o = s then
47           begin
48             writeln(h[k,i].t);
49             f := true;
50             break;
51           end;
52        if not f then writeln('eh');
53     end;
54 end;
55 
56 begin
57   init;
58 end.

RS Hash Function

 1 function RSHash(s1:string):dword;        //qword used;
 2     var
 3       a:qword;     //unsigned int a = 63689;
 4         b:dword;
 5         hash:qword; //unsigned int hash = 0;
 6         i:integer;
 7     begin
 8       a:=63689;
 9         b:=378551;
10         hash:=0;
11 
12       for i:=1 to length(s1) do
13         begin
14           hash:=(hash*a+ord(s1[i])) and $FFFFFFFF;
15             a:=(a*b) and $FFFFFFFF;
16           end;
17 
18         RSHash:=hash and $7FFFFFFF;      
19       end;

JS Hash Function

 1 function JSHash(s1:string):dword;        //qword used;
 2     var
 3       i:integer;
 4         hash:qword;
 5     begin
 6         hash:=1315423911;
 7         for i:=1 to length(s1) do
 8           hash:=(hash xor ((hash shl 5)+ord(s1[i])+(hash shr 2))) and $FFFFFFFF;
 9         JSHash:=hash and $7FFFFFFF;
10       end;

ELF Hash Function

 1    function ELFHash(s1:string):dword;
 2     var
 3       i:integer;
 4       x:dword;
 5     begin
 6         ELFHash:=0;
 7       x:=0;
 8         for i:=1 to length(s1) do
 9         begin
10           ELFHash:=(ELFHash shl 4)+ord(s1[i]);
11             x:=ELFHash and $F0000000;        //x = hash & 0xF0000000L
12             if x<>0 then
13             begin
14               ELFHash:=ELFHash xor (x shr 24);
15                 ELFHash:=ELFHash and not x;
16               end;
17           end;
18         ELFHash:=ELFHash and $7FFFFFFF;
19       end;

BKDR Hash Function

 1 function BKDRHash(s1:string):dword;      //qword used;
 2     var
 3       i:integer;
 4        seed:dword;
 5         hash:qword; 
 6       begin
 7       seed:=131; // 31 131 1313 13131 131313 etc..
 8         hash:=0;
 9         for i:=1 to length(s1) do
10           hash:=(hash*seed+ord(s1[i])) and $FFFFFFFF;
11         BKDRHash:=hash and $7FFFFFFF;
12       end;

DJB Hash Function

 1 function DJBHash(s1:string):dword;       //qword used;
 2     var
 3       i:integer;
 4         hash:qword;
 5     begin
 6         hash:=5381;
 7         for i:=1 to length(s1) do
 8           hash:=(hash+(hash shl 5)+ord(s1[i])) and $FFFFFFFF;
 9         DJBHash:=hash and $7FFFFFFF;
10       end;

AP Hash Function

 1 function APHash(s1:string):dword;
 2     var
 3       i:integer;
 4       begin
 5      APHash:=0;
 6         for i:=1 to length(s1) do
 7       if i and 1=1 then
 8           APHash:=APHash xor ((APHash shl 7) xor ord(s1[i]) xor (APHash shr 3))
 9       else
10           APHash:=APHash xor (not ((APHash shl 11) xor ord(s1[i]) xor (APHash shr 5)));
11         APHash:=APHash and $7FFFFFFF; 
12       end;

SDBM Hash Function

 1 function SDBMHash(s1:string):dword;      //qword used;
 2     var
 3       i:integer;
 4         hash:qword;
 5       begin
 6         hash:=0;
 7       for i:=1 to length(s1) do
 8           hash:=(ord(s1[i])+(hash shl 6)+(hash shl 16)-hash) and $FFFFFFFF;
 9         SDBMHash:=hash and $7FFFFFFF;
10       end;

除题目代码为本人所为，其余皆出自：http://hi.baidu.com/satily/blog/item/5f5ac3fcdaae09fbfc037fcb.html