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(*
Challenge 119
TASK #2 - Sequence without 1-on-1
Submitted by: Cheok-Yin Fung
Write a script to generate sequence starting at 1. Consider the increasing
sequence of integers which contain only 1's, 2's and 3's, and do not have any
doublets of 1's like below. Please accept a positive integer $N and print the
$Nth term in the generated sequence.
1, 2, 3, 12, 13, 21, 22, 23, 31, 32, 33, 121, 122, 123, 131, ...
Example
Input: $N = 5
Output: 13
Input: $N = 10
Output: 32
Input: $N = 60
Output: 2223
*)
program ch2(input, output);
uses sysutils;
function nextSeq(n: Integer): Integer;
function numOk(n: Integer): Boolean;
var
lastDigit, digit: Integer;
begin
if n <= 0 then
numOk := False
else begin
numOk := True;
digit := 0;
while n > 0 do begin
lastDigit := digit;
digit := n mod 10;
n := n div 10;
if (digit < 1) or (digit > 3)
or ((digit = 1) and (lastDigit = 1)) then
numOk := False;
end;
end;
end;
begin
repeat
n := n + 1;
until numOk(n);
nextSeq := n;
end;
var
num, i, n: Integer;
begin
num := StrToInt(paramStr(1));
n := 0;
for i := 1 to num do
n := nextSeq(n);
WriteLn(n);
end.
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