Palabra Tribonacci

Como la palabra de Fibonacci , una palabra de Tribonacci. es una secuencia específica de dígitos. La palabra de Tribonacci se forma por concatenación repetida de la misma manera que la palabra de Fibonacci se forma por adición repetida. Pero a diferencia de la palabra Fibonacci, la palabra Tribonacci está formada por la adición repetida de los últimos tres términos y tiene sus tres primeros términos diferentes entre sí.
 

In Tribonacci word,
  S(0) = 1, 
  S(1) = 12, 
  S(2) = 1213,
  S(3) = 1213121 
  ..... 
where S(n) = S(n-1) + S(n-2) + S(n-3) and + 
represents the concatenation of 
strings. 

La tarea es encontrar la enésima palabra de Tribonacci para un número dado n.
Ejemplos: 
 

// C++ program for nth Fibonacci word
#include <bits/stdc++.h>
using namespace std;
  
// Returns n-th Tribonacci word
string tribWord(int n) {
  string Sn_1 = "1";
  string Sn_2 = "12";
  string Sn_3 = "1213";
  string tmp;
  for (int i = 3; i <= n; i++) {
    tmp = Sn_3;
    Sn_3 += (Sn_2 + Sn_1);
    Sn_1 = Sn_2;
    Sn_2 = tmp;
  }
  
  return Sn_3;
}
  
// driver program
int main() {
  int n = 6;
  cout << tribWord(n);
  return 0;
}

// program for nth Tribonacci word
class GFG {
  
// Returns n-th Tribonacci word
static String tribWord(int n) {
    String Sn_1 = "1";
    String Sn_2 = "12";
    String Sn_3 = "1213";
    String tmp;
    for (int i = 3; i <= n; i++) {
    tmp = Sn_3;
    Sn_3 += (Sn_2 + Sn_1);
    Sn_1 = Sn_2;
    Sn_2 = tmp;
    }
  
    return Sn_3;
}
  
// Driver code
public static void main(String[] args) {
    int n = 6;
    System.out.print(tribWord(n));
}
}
// This code is contributed by Anant Agarwal.

# Python3 Program for nth
# Tribonacci word
  
# Returns n-th Tribonacci word
def tribWord(n):
    Sn_1 = "1"
    Sn_2 = "12"
    Sn_3 = "1213"
    for i in range(3, n+1):
        tmp = Sn_3
        Sn_3 += (Sn_2 + Sn_1)
        Sn_1 = Sn_2
        Sn_2 = tmp
  
    return Sn_3
  
# Driver code
n = 6
print(tribWord(n))
  
# This code is contributed By Anant Agarwal.

// C# program for nth Tribonacci word
using System;
  
class GFG {
  
    // Returns n-th Tribonacci word
    static string tribWord(int n)
    {
        string Sn_1 = "1";
        string Sn_2 = "12";
        string Sn_3 = "1213";
        string tmp;
          
        for (int i = 3; i <= n; i++) {
            tmp = Sn_3;
            Sn_3 += (Sn_2 + Sn_1);
            Sn_1 = Sn_2;
            Sn_2 = tmp;
        }
      
        return Sn_3;
    }
      
    // Driver code
    public static void Main() {
          
        int n = 6;
          
        Console.WriteLine(tribWord(n));
    }
}
  
// This code is contributed by vt_m.

<?php
  
// Returns n-th Tribonacci word
function tribWord($n) 
{
$Sn_1 = "1";
$Sn_2 = "12";
$Sn_3 = "1213";
$tmp;
for ($i = 3; $i <= $n; $i++) 
{
    $tmp = $Sn_3;
    $Sn_3 .= ($Sn_2.$Sn_1);
    $Sn_1 = $Sn_2;
    $Sn_2 = $tmp;
}
  
return $Sn_3;
}
  
// Driver Code
$n = 6;
echo tribWord($n);
  
// This code is contributed by mits 
  
?>

<script>
  
// javascript program for nth Fibonacci word
  
// Returns n-th Tribonacci word
function tribWord(n) {
  var Sn_1 = "1";
  var Sn_2 = "12";
  var Sn_3 = "1213";
  var tmp;
  for (var i = 3; i <= n; i++) {
    tmp = Sn_3;
    Sn_3 += (Sn_2 + Sn_1);
    Sn_1 = Sn_2;
    Sn_2 = tmp;
  }
  
  return Sn_3;
}
  
// driver program
var n = 6;
document.write( tribWord(n));
  
// This code is contributed by noob2000.
</script>