Hosoya’s Triangle

The Fibonnaci triangle or Hosoya’s triangle is a triangular arrangement of numbers based on Fibonacci numbers. Each number is the sum of two numbers above in either the left diagonal or the right diagonal. The first few rows are:

The numbers in this triangle follow the recurrence relations

Relation to Fibonacci numbers
The entries in the triangle satisfy the identity

Thus, the two outermost diagonals are the Fibonacci numbers, while the numbers on the middle vertical lines are the squares of the Fibonacci numbers. All the other numbers in the triangle are the product of two distinct Fibonacci numbers greater than 1. The row sums are the first convolved Fibonnaci numbers.

Sources : Stackoverflow, Wikipedia

Given a positive integers n. The task is print Hosoya’s triangle of size n.
Examples:

Input : n = 4
Output :
1
1 1
2 1 2
3 2 2 3

Input : n = 5
Output :
1
1 1
2 1 2
3 2 2 3
5 3 4 3 5



Below is the implementation of printing Hosoya’s triangle of height n:

C++

// CPP Program to print Hosoya's
// triangle of height n.
#include <bits/stdc++.h>
using namespace std;
  
int Hosoya(int n, int m)
{
    // Base case
    if ((n == 0 && m == 0) ||
        (n == 1 && m == 0) || 
        (n == 1 && m == 1) ||
        (n == 2 && m == 1))
        return 1;
  
    // Recursive step
    if (n > m)
        return Hosoya(n - 1, m) 
               + Hosoya(n - 2, m);
  
    else if (m == n)
        return Hosoya(n - 1, m - 1) 
               + Hosoya(n - 2, m - 2);
  
    else
        return 0;
}
  
// Print the Hosoya triangle of height n.
void printHosoya(int n)
{
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= i; j++) 
            cout << Hosoya(i, j) << " ";     
  
        cout << endl;
    }
}
  
// Driven Program
int main()
{
    int n = 5;
    printHosoya(n);
    return 0;
}

Java

// Java Program to print Hosoya's 
// triangle of height n.
import java.util.*;
  
class GFG {
      
    static int Hosoya(int n, int m)
    {
        // Base case
        if ((n == 0 && m == 0) ||
            (n == 1 && m == 0) || 
            (n == 1 && m == 1) || 
            (n == 2 && m == 1))
            return 1;
       
        // Recursive step
        if (n > m)
            return Hosoya(n - 1, m)
                   + Hosoya(n - 2, m);
              
        else if (m == n)
            return Hosoya(n - 1, m - 1)
                    + Hosoya(n - 2, m - 2);
              
        else
            return 0;
    }
       
    // Print the Hosoya triangle of height n.
    static void printHosoya(int n)
    {
        for (int i = 0; i < n; i++)
        {
            for (int j = 0; j <= i; j++) 
                System.out.print(Hosoya(i, j) 
                                        + " ");       
       
            System.out.println("");
        }
    }
  
      
    /* Driver program to test above function */
    public static void main(String[] args) 
    {
        int n = 5;
        printHosoya(n);
           
    }
}
  
// This code is contributed by  Arnav Kr. Mandal.

Python3

# Python3 code to print Hosoya's
# triangle of height n.
  
def Hosoya( n , m ):
  
    # Base case
    if ((n == 0 and m == 0) or
        (n == 1 and m == 0) or
        (n == 1 and m == 1) or
        (n == 2 and m == 1)):
                return 1
      
    # Recursive step
    if n > m:
        return Hosoya(n - 1, m) 
                    + Hosoya(n - 2, m)
  
    elif m == n:
        return Hosoya(n - 1, m - 1
                        + Hosoya(n - 2,    m - 2)
  
    else:
        return 0
          
# Print the Hosoya triangle of height n.
def printHosoya( n ):
    for i in range(n):
        for j in range(i + 1):
            print(Hosoya(i, j) , end = " ")
        print("\n", end = "")
          
# Driven Code
n = 5
printHosoya(n)
  
# This code is contributed by "Sharad_Bhardwaj".

C#

// C# Program to print Hosoya's 
// triangle of height n.
using System;
  
class GFG {
      
    static int Hosoya(int n, int m)
    {
        // Base case
        if ((n == 0 && m == 0) ||
            (n == 1 && m == 0) || 
            (n == 1 && m == 1) || 
            (n == 2 && m == 1))
            return 1;
      
        // Recursive step
        if (n > m)
            return Hosoya(n - 1, m)
                 + Hosoya(n - 2, m);
              
        else if (m == n)
            return Hosoya(n - 1, m - 1)
                 + Hosoya(n - 2, m - 2);
              
        else
            return 0;
    }
      
    // Print the Hosoya triangle of height n.
    static void printHosoya(int n)
    {
        for (int i = 0; i < n; i++)
        {
            for (int j = 0; j <= i; j++) 
                Console.Write(Hosoya(i, j) 
                                        + " "); 
      
            Console.WriteLine("");
        }
    }
  
      
    /* Driver program to test above function */
    public static void Main() 
    {
        int n = 5;
          
        printHosoya(n);
          
    }
}
  
// This code is contributed by vt_m.

PHP

<?php
// PHP Program to print Hosoya's
// triangle of height n.
  
function Hosoya(int $n, int $m)
{
    // Base case
    if (($n == 0 && $m == 0) ||
        ($n == 1 && $m == 0) || 
        ($n == 1 && $m == 1) ||
        ($n == 2 && $m == 1))
        return 1;
  
    // Recursive step
    if ($n > $m)
        return Hosoya($n - 1,$m) + 
               Hosoya($n - 2, $m);
  
    else if ($m == $n)
        return Hosoya($n - 1, $m - 1) + 
               Hosoya($n - 2, $m - 2);
  
    else
        return 0;
}
  
// Print the Hosoya 
// triangle of height n.
function printHosoya( $n)
{
    for ( $i = 0; $i < $n; $i++)
    {
        for ( $j = 0; $j <= $i; $j++) 
            echo Hosoya($i, $j) , " "
            echo "\n";
    }
}
  
// Driven Code
$n = 5;
printHosoya($n);
  
// This code is contributed by anuj_67.
?>


Output :

1 
1 1 
2 1 2 
3 2 2 3 
5 3 4 3 5 

Below is the implementation of printing Hosoya’s triangle of height n using Dynamic Programming:

C++

// CPP Program to print Hosoya's triangle of height n.
#include <bits/stdc++.h>
#define N 5
using namespace std;
  
// Print the Hosoya triangle of height n.
void printHosoya(int n)
{
    int dp[N][N];
    memset(dp, 0, sizeof(dp));
  
    // base case.
    dp[0][0] = dp[1][0] = dp[1][1] = 1;
  
    // For each row.
    for (int i = 2; i < n; i++) {
  
        // for each column;
        for (int j = 0; j < n; j++) {
  
            // recursive steps.
            if (i > j)
                dp[i][j] = dp[i - 1][j] + dp[i - 2][j];
  
            else
                dp[i][j] = dp[i - 1][j - 1] + dp[i - 2][j - 2];
        }
    }
  
    // printing the solution
    for (int i = 0; i < n; i++) {
        for (int j = 0; j <= i; j++) 
            cout << dp[i][j] << " ";        
  
        cout << endl;
    }
}
  
// Driven Program
int main()
{
    int n = 5;
    printHosoya(n);
    return 0;
}

Java

// JAVA Code for Hosoya Triangle
import java.util.*;
  
class GFG {
      
    static int N = 5;
      
    // Print the Hosoya triangle 
    // of height n.
    static void printHosoya(int n)
    {
        int dp[][] = new int[N][N];
          
        // base case.
        dp[0][0] = dp[1][0] = 1;
        dp[1][1] = 1;
       
        // For each row.
        for (int i = 2; i < n; i++) 
        {
            // for each column;
            for (int j = 0; j < n; j++) 
            {
                 // recursive steps.
                if (i > j)
                    dp[i][j] = dp[i - 1][j] + 
                                        dp[i - 2][j];
       
                else
                    dp[i][j] = dp[i - 1][j - 1] +
                                    dp[i - 2][j - 2];
            }
        }
       
        // printing the solution
        for (int i = 0; i < n; i++) 
        {
            for (int j = 0; j <= i; j++) 
                System.out.print(dp[i][j] + " ");        
       
            System.out.println("");
        }
    }
      
    /* Driver program*/
    public static void main(String[] args) 
    {
        int n = 5;
        printHosoya(n);
    }
}
  
// This code is contributed by Arnav Kr. Mandal.

C#

// C# Code for Hosoya Triangle
using System;
  
class GFG {
      
    static int N = 5;
      
    // Print the Hosoya triangle 
    // of height n.
    static void printHosoya(int n)
    {
        int [,]dp = new int[N,N];
          
        // base case.
        dp[0,0] = dp[1,0] = 1;
        dp[1,1] = 1;
      
        // For each row.
        for (int i = 2; i < n; i++) 
        {
            // for each column;
            for (int j = 0; j < n; j++) 
            {
                // recursive steps.
                if (i > j)
                    dp[i,j] = dp[i - 1,j] + 
                              dp[i - 2,j];
      
                else
                    dp[i,j] = dp[i - 1,j - 1] 
                           + dp[i - 2,j - 2];
            }
        }
      
        // printing the solution
        for (int i = 0; i < n; i++) 
        {
            for (int j = 0; j <= i; j++) 
                Console.Write(dp[i,j] + " "); 
      
            Console.WriteLine("");
        }
    }
      
    /* Driver program*/
    public static void Main() 
    {
        int n = 5;
          
        printHosoya(n);
    }
}
  
// This code is contributed by Vt_m.

Output :

1 
1 1 
2 1 2 
3 2 2 3 
5 3 4 3 5 


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Improved By : vt_m