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MODULE Ch2 EXPORTS Main;
IMPORT SIO,Text;
PROCEDURE QuickSort(VAR A:ARRAY OF INTEGER;Left,Right:INTEGER) =
VAR
I,J:INTEGER;
Pivot,Temp:INTEGER;
BEGIN
I := Left;
J := Right;
Pivot := A[(Left + Right) DIV 2];
REPEAT
WHILE Pivot < A[I] DO INC(I) END;
WHILE Pivot > A[J] DO DEC(J) END;
IF I <= J THEN
Temp := A[I];
A[I] := A[J];
A[J] := Temp;
INC(I);
DEC(J);
END;
UNTIL I > J;
IF Left < J THEN QuickSort(A, Left, J) END;
IF I < Right THEN QuickSort(A, I, Right) END;
END QuickSort;
PROCEDURE FrequencyEqualizer(Str:TEXT):BOOLEAN =
VAR
Freq:ARRAY[0..25] OF INTEGER;
Arr:REF ARRAY OF INTEGER;
J,Count:INTEGER;
BEGIN
J := 0;
Count := 0;
FOR I := FIRST(Freq) TO LAST(Freq) DO Freq[I] := 0 END;
FOR I := 0 TO Text.Length(Str)-1 DO
INC(Freq[ORD(Text.GetChar(Str,I)) - ORD('a')])
END;
FOR I := FIRST(Freq) TO LAST(Freq) DO IF Freq[I] # 0 THEN INC(Count) END END;
Arr := NEW(REF ARRAY OF INTEGER,Count);
<*ASSERT Arr # NIL *>
FOR I := FIRST(Freq) TO LAST(Freq) DO
IF Freq[I] # 0 THEN
Arr[J] := Freq[I];
INC(J);
END
END;
QuickSort(Arr^,FIRST(Arr^),LAST(Arr^));
IF(Arr[0] = Arr[1]+1) AND (Arr[LAST(Arr^)] = Arr[1]) THEN
RETURN TRUE
END;
RETURN FALSE;
END FrequencyEqualizer;
BEGIN
SIO.PutBool(FrequencyEqualizer("abbc")); SIO.Nl();
SIO.PutBool(FrequencyEqualizer("xyzyyxz")); SIO.Nl();
SIO.PutBool(FrequencyEqualizer("xzxz")); SIO.Nl();
END Ch2.
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