Recursive program to print triangular patterns

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We have discussed iterative pattern printing in previous post.

Examples:

Input : 7
Output :                    
      *
     * *
    * * *
   * * * * 
  * * * * *
 * * * * * *
* * * * * * *

Algorithm:-
step 1:- first think for the base condition i.e. number less than 0
step 2:-do the recursive calls till number less than 0 i.e:- printPartten(n-1, k+1);
step 3:-print the spaces
step 4:-then print * till number

Below is the implementation of above approach:

C++

// C++ program to print triangular patterns using Recursive 
#include <iostream> 
  
using namespace std; 
void printPartten(int n, int k) 
{ 
    if (n < 0) // Base condition 
        return; 
  
    // Recursive call 
    printPartten(n - 1, k + 1);  
  
    int i; 
    for (i = 0; i < k; i++) // it makes spaces 
        cout << " "; 
    for (i = 0; i < n; i++) // for print * 
        printf("* "); 
    printf("\n"); // for next line 
} 
  
int main() 
{ 
    int n = 7; 
  
    // Call to printPartten function 
    printPartten(n, 0);  
    return 0; 
} 

Java

// Java program to print triangular patterns using Recursive 
import java.io.*; 
public class GFG{  
static void printPartten(int n, int k)  
{  
    if (n < 0) // Base condition  
        return;  
  
    // Recursive call  
    printPartten(n - 1, k + 1);  
  
    int i;  
    for (i = 0; i < k; i++) // it makes spaces  
        System.out.printf(" ");  
    for (i = 0; i < n; i++) // for print *  
        System.out.printf("* ");  
    System.out.printf("\n"); // for next line  
}  
  
public static void main(String[]args)  
{  
    int n = 7;  
  
    // Call to printPartten function  
    printPartten(n, 0);  
}  
}  

Python3

# Python 3 program to print triangular 
# patterns using Recursive 
  
def printPartten(n, k): 
      
    if (n < 0): # Base condition 
        return; 
  
    # Recursive call 
    printPartten(n - 1, k + 1);  
  
    for i in range(0, k): # it makes spaces 
        print(" ", end=""); 
    for i in range(0, n): # for print * 
        print("* ", end = ""); 
    print("\n", end=""); # for next line 
  
# Driver Code 
n = 7; 
  
# Call to printPartten function 
printPartten(n, 0);  
  
# This code is contributed  
# by Akanksha Rai 

C#

// C# program to print triangular 
// patterns using Recursive 
using System; 
  
class GFG 
{  
static void printPartten(int n, int k)  
{  
    if (n < 0) // Base condition  
        return;  
  
    // Recursive call  
    printPartten(n - 1, k + 1);  
  
    int i;  
    for (i = 0; i < k; i++) // it makes spaces  
        Console.Write(" ");  
    for (i = 0; i < n; i++) // for print *  
        Console.Write("* ");  
    Console.Write("\n"); // for next line  
}  
  
// Driver Code 
public static void Main()  
{  
    int n = 7;  
  
    // Call to printPartten function  
    printPartten(n, 0);  
}  
}  
  
// This code is contributed  
// by Subhadeep

PHP

<?php 
// PHP program to print triangular 
// patterns using Recursive  
  
function printPartten($n, $k)  
{  
    if ($n < 0) // Base condition  
        return;  
  
    // Recursive call  
    printPartten($n - 1, $k + 1);  
  
    for ($i = 0; $i < $k; $i++) // it makes spaces  
        echo " ";  
    for ($i = 0; $i < $n; $i++) // for print *  
        echo ("* ");  
    echo ("\n"); // for next line  
}  
  
// Driver Code 
$n = 7;  
  
// Call to printPartten function  
printPartten($n, 0);  
  
// This code is contributed by jit_t 
?> 

Javascript

<script> 
// javascript program to print triangular patterns using Recursive 
  
    function printPartten(n , k) { 
        if (n < 0) // Base condition 
            return; 
  
        // Recursive call 
        printPartten(n - 1, k + 1); 
  
        var i; 
        for (i = 0; i < k; i++) // it makes spaces 
             document.write(" "); 
        for (i = 0; i < n; i++) // for print * 
             document.write("* "); 
         document.write("<br/>"); // for next line 
    } 
  
      
        var n = 7; 
  
        // Call to printPartten function 
        printPartten(n, 0); 
  
// This code is contributed by Rajput-Ji 
</script> 

Output:

      * 
     * * 
    * * * 
   * * * * 
  * * * * * 
 * * * * * * 
* * * * * * *

Time Complexity: O(n²)
Auxiliary Space: O(n), The extra space is used in recursion call stack.

How to print its reverse pattern?
simply Just put the recursive line end of the function

Example:

Input : 7
Output : 
* * * * * * *
 * * * * * * 
  * * * * *    
   * * * *  
    * * *    
     * *          
      *

C++

// C++ program to print reverse triangular  
// patterns using Recursive 
#include <bits/stdc++.h> 
using namespace std; 
  
void printPartten(int n, int k) 
{ 
    if (n < 0) // Base condition 
        return; 
    int i; 
    for (i = 0; i < k; i++) // it makes spaces 
        cout <<" "; 
    for (i = 0; i < n; i++) // for print * 
        cout <<"* "; 
    cout <<"\n"; // for next line 
  
    // Recursive calls 
    printPartten(n - 1, k + 1);  
} 
  
int main() 
{ 
    int n = 7; 
  
    // Call to printPartten function 
    printPartten(n, 0);  
    return 0; 
} 
// this code is contributed by shivanisinghss2110

C

// C program to print reverse triangular  
// patterns using Recursive 
#include <stdio.h> 
#include <stdlib.h> 
  
void printPartten(int n, int k) 
{ 
    if (n < 0) // Base condition 
        return; 
    int i; 
    for (i = 0; i < k; i++) // it makes spaces 
        printf( " "); 
    for (i = 0; i < n; i++) // for print * 
        printf("* "); 
    printf("\n"); // for next line 
  
    // Recursive calls 
    printPartten(n - 1, k + 1);  
} 
  
int main() 
{ 
    int n = 7; 
  
    // Call to printPartten function 
    printPartten(n, 0);  
    return 0; 
} 

Java

// Java program to print reverse triangular  
// patterns using Recursive  
import java.io.*; 
public class GFG{  
static void printPartten(int n, int k)  
{  
    if (n < 0) // Base condition  
        return;  
    int i;  
    for (i = 0; i < k; i++) // it makes spaces  
        System.out.print(" ");  
    for (i = 0; i < n; i++) // for print *  
        System.out.print("* ");  
    System.out.print("\n"); // for next line  
  
    // Recursive calls  
    printPartten(n - 1, k + 1);  
}  
  
public static void main(String[] args)  
{  
    int n = 7;  
  
    // Call to printPartten function  
    printPartten(n, 0);  
} 
}  

Python 3

# Python 3 program to print reverse  
# triangular patterns using Recursive 
  
def printPartten(n, k): 
  
    if (n < 0): # Base condition 
        return; 
    for i in range(0, k): # it makes spaces 
        print(" ", end = "") 
    for i in range(0, n): # for print * 
        print("*", end = " ") 
    print("\n", end = "") # for next line 
  
    # Recursive calls 
    printPartten(n - 1, k + 1);  
  
# Driver Code 
n = 7; 
  
# Call to printPartten function 
printPartten(n, 0);  
  
# This code is contributed  
# by Akanksha Rai 

C#

// C# program to print reverse triangular  
// patterns using Recursive  
using System; 
  
class GFG 
{  
static void printPartten(int n, int k)  
{  
    if (n < 0) // Base condition  
        return;  
    int i;  
    for (i = 0; i < k; i++) // it makes spaces  
        Console.Write(" ");  
    for (i = 0; i < n; i++) // for print *  
        Console.Write("* ");  
    Console.Write("\n"); // for next line  
  
    // Recursive calls  
    printPartten(n - 1, k + 1);  
}  
  
// Driver Code 
public static void Main()  
{  
    int n = 7;  
  
    // Call to printPartten function  
    printPartten(n, 0);  
}  
}  
  
// This code is contributed  
// by PrinciRaj1992 

PHP

<?php 
// PHP program to print reverse triangular  
// patterns using Recursive  
function printPartten($n, $k)  
{  
    if ($n < 0) // Base condition  
        return;  
  
    for ($i = 0; $i < $k; $i++) // it makes spaces  
        echo(" ");  
    for ($i = 0; $i < $n; $i++) // for print *  
        echo("* ");  
    echo("\n"); // for next line  
  
    // Recursive calls  
    printPartten($n - 1, $k + 1);  
}  
  
// Driver Code 
$n = 7;  
  
// Call to printPartten function  
printPartten($n, 0);  
  
// This code is contributed  
// by Mukul singh 
?> 

Javascript

<script> 
// C++ program to print reverse triangular  
// patterns using Recursive 
  
function printPartten(n, k) 
{ 
    if (n < 0) // Base condition 
        return; 
    let i; 
    for (i = 0; i < k; i++) // it makes spaces 
        document.write(" "); 
    for (i = 0; i < n; i++) // for print * 
        document.write("* "); 
    document.write("<br>"); // for next line 
  
    // Recursive calls 
    printPartten(n - 1, k + 1);  
} 
  
//driver code 
    let n = 7; 
  
    // Call to printPartten function 
    printPartten(n, 0);  
   
// this code is contributed by shivanisinghss2110  
</script>

Output:

* * * * * * * 
 * * * * * * 
  * * * * * 
   * * * * 
    * * * 
     * * 
      *

Time Complexity: O(n²)
Auxiliary Space: O(1), As the function becomes tail recursive no extra stack space is required.

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