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<![CDATA[
program wc( input, output );
const MAXPATLEN = 5;
const MAXTEXTLEN = 1000;
const MAXCHAR = 127;
type PATTERN = packed array [1..MAXPATLEN] of char;
TEXT = packed array [1..MAXTEXTLEN] of char;
var pat: PATTERN;
text: TEXT;
pos: integer;
function search( pat: PATTERN; text: TEXT ): integer;
var i, j, k, m, n: integer;
skip: array [0..MAXCHAR] of integer;
found: boolean;
begin
found := FALSE; search := 0;
m := length(pat);
if m=0 then begin
search := 1;
found := TRUE;
end;
for k:=0 to MAXCHAR do skip[k] := m; { Preprocessing }
for k:=1 to m-1 do skip[ord(pat[k])] := m-k;
n := length(text); { Search }
writeln( 'pat ', pat, ' text = ', text );
writeln( 'm = ', m, 'n = ', n );
k := m;
while not found and (k <= n) do begin
i := k; j := m;
while (j >= 1) do
if text[i] <> pat[j] then j := -1
else begin
j := j-1; i := i-1;
end;
if j = 0 then begin
search := i+1;
found := TRUE;
end;
k := k + skip[ord(text[k])];
end;
end;
begin
{ while not eof(f) do begin read(pat); read(text); }
pos := search('aaaab','aaaa5aaa9aaaab');
writeln( 'pattern found at ', pos );
{ end; }
end.
]]> |
Pascal source (713.wc.p) 