program selectionSort;
function maxValueIndex(var a : array of integer; minIndex, maxIndex : integer);
{Pre: 	a defined
		maxIndex>=minIndex;
		minIndex>=0;
		a[minIndex..maxIndex] defined
 Post:	for each i into minIndex..maxIndex, a[maxIndex] >= a[i] 
}
var tempMax : integer;
begin
	if minIndex >= maxIndex then maxValueIndex := minIndex;
	else begin
		tempMax := maxValueIndex(a, minIndex+1, maxIndex);
		if a[minIndex]<a[tempMax]
			then maxValueIndex := tempMax;
			else maxValueIndex := minIndex;
		end
end;
procedure swap(var a : array of integer; i, j : integer);
{Pre: 	a defined
		j>i;
		i>=0;
		a[i] defined
		a[j] defined
 Post:	a[i]=old value at a[j] et a[j]=old value at a[i] 
}
var temp: integer;
begin
	temp := a[i];
	a[i] := a[j];
	a[j] := temp;
end;
procedure selectionSort(var a : array of integer; arraySize : integer);
{Pre: 	a defined
		arraySize>=0;
		a indexed from 0 to arraySize -1
		for each i into 0..arraySize-1, a[i] defined
 Post:	for each i into 0..arraySize-2, a[i] <= a[i+1]
}
var i : integer;
begin
	for i := arraySize downto 0 do
		swap(a, i, maxValueIndex(a,1,i));
end;
{main program
}
begin
	const maxIndice = 7;
	var testArray : packed array[0..maxIndice] of integer;
	testArray[0] := 8;
	testArray[1] := 4;
	testArray[2] := 6;
	testArray[3] := 2;
	testArray[4] := 13;
	testArray[5] := 4;
	testArray[6] := 1;
	testArray[7] := 20;
	var i : integer;
	writeln('Unsorted array :');
	for i:=0 to maxIndice do
		writeln('value ', testArray[i], ' at index ', i);
	selectionSort(testArray, maxIndice+1);
	writeln('Sorted array :');
	for i:=0 to maxIndice do
		writeln('value ', testArray[i], ' at index ', i);
end.