这个快排用的是随机数优化，防止有些出题人卡快排

var
  a:array[0..1000000] of longint;
  i,j,k,n,m:longint;
procedure sort(l,r:longint);
var
  i,j,mid,t:longint;
begin
  if l>r then exit;
  i:=l; j:=r;
  mid:=a[random(r-l+1)+l];
  repeat
    while a[i]mid do dec(j);
    if i<=j then
      begin
        t:=a[i];
        a[i]:=a[j];
        a[j]:=t;
        inc(i); dec(j);
      end;
  until i>j;
  if j>l then sort(l,j);
  if i