Разобрать код сортировки массива

procedure sort_quick_int(var a: array of integer);
procedure sort(var ar: array of integer; low, high: integer);
 
var
i, j: integer;
m, wsp: integer;
 
begin
i := low;j := high;m := ar[(i + j) div 2];
repeat
while ar[i] < m do Inc(i);
while ar[j] > m do Dec(j);
if i <= j then begin
wsp := ar[i];ar[i] := ar[j];ar[j] := wsp;
Inc(i);Dec(j);
end;
until i > j;
if low < j then sort(ar, low, j);
if i < high then sort(ar, i, high);
end;
 
 
begin
sort(a, 0, length(a) - 1);
end;
 
 
procedure pair_sort_quick_int(var a,b: array of integer);
procedure sort(var ar,b: array of integer; low, high: integer);
var
i, j: integer;
m, wsp: integer;
begin
i := low;j := high;m := ar[(i + j) div 2];
repeat
while ar[i] < m do Inc(i);
while ar[j] > m do Dec(j);
if i <= j then begin
wsp := ar[i];ar[i] := ar[j];ar[j] := wsp;
wsp := b[i];b[i] := b[j];b[j] := wsp;
Inc(i);Dec(j);
end;
until i > j;
if low < j then sort(ar,b, low, j);
if i < high then sort(ar,b, i, high);
end;
 
begin
sort(a,b, 0, length(a) - 1);
end;
 
 
const
max_a=15;
var
a,b,c:array of integer;
i,j,n:integer;
begin
SetLength(a,max_a);
for i:=0 to max_a-1 do begin
a[i]:=random(10)-0;
write(a[i]:4);
end;
 
sort_quick_int(a);
SetLength(b,1);
SetLength(c,1);
n:=0;
b[n]:=a[0];
c[n]:=1;
i:=1;
while i<max_a do
begin
if a[i]=b[n] then inc(c[n])
else
begin
inc(n);
SetLength(b,n+1);
SetLength(c,n+1);
b[n]:=a[i];
c[n]:=1;
end;
inc(i)
end;
 
pair_sort_quick_int(c,b);
 
n:=0;
for i:=length(b)-1 downto 0 do
begin
//writeln(b[i],' ',c[i]);
for j:=1 to c[i] do
begin
a[n]:=b[i];
inc(n);
end;
end;
writeln;
for i:=0 to max_a-1 do begin
write(a[i]:4);
end;
readln;
 
end.