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Random numbers

Posted on 2004-04-05
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Last Modified: 2010-04-16
i wrote a small example  a program to make it clear for you guys

for x := 1 to 5 do
begin
write('wtite a number : ') ;
readln(number)
end
for x := 1 to 5 do
writeln(number)

i want it to random then number by size after, like if i enter
5  , 1 ,  6 ,  7 , 2 the result will be
1 , 2 , 5 , 6 , 7  

any clue ?
0
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Question by:blasta
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10 Comments
 
LVL 101

Expert Comment

by:mlmcc
ID: 10762983
You want to SORT the numbers.  This sounds like a home work assignment, is it?

Can you use arrays? I suspect not from the sample code.

Basic algorithm
Compare A & B
Swap if out of order
Compare B & C
Swap if out of order
...
Repeat until no swaps

mlmcc
0
 
LVL 11

Expert Comment

by:ZhaawZ
ID: 10763727
Something from the examples (with some changes), which came with Borland Pascal:

program sorting;

uses
  wincrt;

var
  numbers : array [1..16384] of integer;
  max : word;
  n : integer;

procedure Sort(var arr : array of integer; l, r: Integer);
var
  i, j, x, y: integer;
begin
  i := l;
  j := r;
  x := arr[(l+r) div 2];
  repeat
    while arr[i] < x do i := i + 1;
    while x < arr[j] do j := j - 1;
    if i <= j then begin
      y := arr[i];
      arr[i] := arr[j];
      arr[j] := y;
      i := i + 1;
      j := j - 1;
    end;
  until i > j;
  if l < j then Sort(arr, l, j);
  if i < r then Sort(arr, i, r);
end;

begin
write('How many numbers? : '); readln(max);
for n := 1 to max do begin
  write('write a number (', n, '): ');
  readln(numbers[n]);
end;
clrscr;
for n := 1 to max do write(numbers[n]:6);
writeln;
sort(numbers, 0, max - 1);
for n := 1 to max do write(numbers[n]:6);
end.
0
 

Author Comment

by:blasta
ID: 10765544
thanks guys but i was looking for a shorter answer , yes i can use array  ... but i'll wait to find if there is a shorter way to do it ...
0
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LVL 11

Expert Comment

by:ZhaawZ
ID: 10768911
Much slower example than the previous one, but.. It's shorter ;) and easier to understand, I think.

program sorting;

uses
  wincrt;

var
  max : word;
  arr : array [1..16384] of integer;
  tmp : integer;
  n : integer;

begin
write('How many numbers? : '); readln(max);
for n := 1 to max do begin
  write('write a number (', n, '): ');
  readln(arr[n]);
end;
clrscr;
for n := 1 to max do write(arr[n]:6);
writeln;
for n := 1 to max - 1 do begin {start sorting}
  if arr[n] > arr[n+1] then begin
    tmp := arr[n];
    arr[n] := arr[n+1];
    arr[n+1] := tmp;
    if n > 1 then n := n - 2;
  end;
end; {end sorting}
for n := 1 to max do write(arr[n]:6);
end.
0
 
LVL 3

Accepted Solution

by:
Aliev earned 500 total points
ID: 10785267
const
N=5;
var
mas:array[1..N] of integer;
i,j,k:integer;
begin

for i:=1 to N do
read(mas[i]);


for i:=1 to N do begin
     for j:=1 to N do begin
         if mas[i]<mas[j] then begin k:=mas[i]; mas[i]:=mas[j]; mas[j]:=k; end;
     end;      
end;



end.
0
 
LVL 1

Expert Comment

by:xtremecris
ID: 10801238
The shortest&fastest way to sort an array of numbers is not QuickSort, or RadixSort for that matter.

If you have numbers which are smaller than, let's say, 1000 you can sort them like this:
- use an array but not for saving the actuall numbers to memory, instead you save their frequency;
- when you read the number N from the keyboard you update the frequency like this:
    freq[N]:=freq[N]+1;
  or simply:
    inc(freq[N]);
- when you want to print the numbers you simply go throw all the numbers form 0 to 1000 with I in a FOR statement and if freq[I]>0 then you print I once(if freq[I]=i), twice(if freq[I]=2) and so on... Of course that can be done with an other FOR statement.

I do not aprove with the habit of others that solve your homework instead of explaing it to you... I hope the admins will take action in this matter!

Anyway if you have a question regarding what I said simply ask.

Best regards,
Cris.
0
 
LVL 1

Expert Comment

by:xtremecris
ID: 10802380
Okay, I see that you accepted an answer which solved your homework.
I'll give you my program too: it's shorter, and faster if you have a lot of numbers:

const Max=32000;
var
freq:array[1..Max] of integer;
i,j,k:integer;
begin
readln(n);
for i:=1 to N do
 begin
  read(j);
  inc(freq[j]);
 end;

for i:=0 to Max do
     for j:=1 to freq[i] do
       Write(j,' ');  
end;
0
 
LVL 101

Expert Comment

by:mlmcc
ID: 11229488
Netminder:
Why the comment?

Having been an educator and given an assignment very much like this one, I was curious.  I also note he never responded to the question nor did he seem offended by it.

Pascal is a TA fraught with homework questions since Pascal is one of the primary teaching tools.  I realize it is used commercially but its original intent and was as a teaching tool and not for building applications for commercial use.

mlmcc
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