Recursive program to print triangular patterns

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.