Modula 2 :: QSORT

MODULE Test;

IMPORT STextIO, SWholeIO, RandomNumber;

VAR
    a: ARRAY [1..10] OF CARDINAL;
    i: CARDINAL;

PROCEDURE QSORT(l, r: CARDINAL);
VAR
    i, j: CARDINAL;
    x, y: CARDINAL;
BEGIN
    i := l;
    j := r;
    x := a[l + RandomNumber.RandomCard(0, r - l + 1)];
    WHILE i < j DO
        WHILE a[i] < x DO
            i := i + 1;
        END;
        WHILE x < a[j] DO
            j := j - 1;
        END;
        IF i <= j THEN
            y := a[i];
            a[i] := a[j];
            a[j] := y;
            i := i + 1;
            j := j - 1;
        END;
    END;
    IF i < r THEN
        QSORT(i, r);
    END;
    IF l < j THEN
        QSORT(l, j);
    END;
END QSORT;

BEGIN
    FOR i := 1 TO 10 DO
        a[i] := RandomNumber.RandomInt(0, 100);
        SWholeIO.WriteCard(a[i], 0);
        STextIO.WriteChar(' ');
    END;
    STextIO.WriteLn;
    QSORT(1, 10);
    FOR i := 1 TO 10 DO
        SWholeIO.WriteCard(a[i], 0);
        STextIO.WriteChar(' ');
    END;
    STextIO.WriteLn;
END Test.