Program to print hollow Triangle pattern

Last Updated : 13 Mar, 2023

Given the number of lines as N, the task is to form the given hollow Triangle pattern.
Examples:

Input: N = 6  Output:  ************  *****  *****  ****    ****  ***      ***  **        **  *          *

Approach:

Input number of rows to print from the user as N.
To iterate through rows run an outer loop from number of rows till it is greater than 1. The loop structure should look like for(i=N; i>=1; i–).
To print spaces, run an inner loop from i to space (another local variable). The loop structure should look like for(k=1; k=1; j–); .Inside this loop print star.
After printing all columns of a row, move to next line i.e. print new line.

Below is the implementation of the above approach:

C++

   // C++ program for printing 
// the hollow triangle pattern 
  
#include <iostream> 
using namespace std; 
  
// Function for printing pattern 
void pattern(int N) 
{ 
    int i, j, k = 0, space = 1, rows = N; 
  
    // For printing stars 
    for (i = rows; i >= 1; i--) { 
        for (j = 1; j <= i; j++) { 
            cout << "*"; 
        } 
        if (i != rows) { 
            // for printing space 
            for (k = 1; k <= space; k++) { 
                cout << " "; 
            } 
  
            // increment by 2 
            space = space + 2; 
        } 
        for (j = i; j >= 1; j--) { 
            if (j != rows) 
                cout << "*"; 
        } 
        cout << "\n"; 
    } 
    cout << "\n"; 
} 
  
// Driver code 
int main() 
{ 
  
    // Get N 
    int N = 6; 
  
    // Print the pattern 
    pattern(N); 
  
    return 0; 
} 
 
  

C

   // C program for printing 
// the hollow triangle pattern 
  
#include <stdio.h> 
  
// Function for printing pattern 
void pattern(int N) 
{ 
    int i, j, k = 0, space = 1, rows = N; 
  
    // For printing stars 
    for (i = rows; i >= 1; i--) { 
        for (j = 1; j <= i; j++) { 
            printf("*"); 
        } 
        if (i != rows) { 
            // for printing space 
            for (k = 1; k <= space; k++) { 
                printf(" "); 
            } 
  
            // increment by 2 
            space = space + 2; 
        } 
        for (j = i; j >= 1; j--) { 
            if (j != rows) 
                printf("*"); 
        } 
        printf("\n"); 
    } 
    printf("\n"); 
} 
  
// Driver code 
int main() 
{ 
  
    // Get N 
    int N = 6; 
  
    // Print the pattern 
    pattern(N); 
  
    return 0; 
} 
 
  

Java

   // Java program for printing 
// the hollow triangle pattern 
import java.util.*; 
  
class solution 
{ 
  
// Function for printing pattern 
static void pattern(int N) 
{ 
    int i, j, k = 0, space = 1, rows = N; 
  
    // For printing stars 
    for (i = rows; i >= 1; i--) { 
        for (j = 1; j <= i; j++) { 
            System.out.print("*"); 
        } 
        if (i != rows) { 
            // for printing space 
            for (k = 1; k <= space; k++) { 
            System.out.print(" "); 
            } 
  
            // increment by 2 
            space = space + 2; 
        } 
        for (j = i; j >= 1; j--) { 
            if (j != rows) 
                System.out.print("*"); 
        } 
        System.out.print("\n"); 
    } 
    System.out.print("\n"); 
} 
  
// Driver code 
public static void main(String args[]) 
{ 
  
    // Get N 
    int N = 6; 
  
    // Print the pattern 
    pattern(N); 
  
}  
} 
  
//This code is contributed by Surendra_Gangwar 
 
  

Python3

   # Python 3 program for printing  
# the hollow triangle pattern  
  
# Function for printing pattern 
def pattern(N): 
    k, space, rows = 0, 1, N 
  
    # For printing stars  
    for i in range(rows, 0, -1): 
        for j in range(1, i + 1): 
            print('*', end = '') 
  
        if i != rows: 
            # for printing space  
            for k in range(1, space + 1): 
                print(' ', end = '') 
  
            # increment by 2  
            space += 2
        for j in range(i, 0, -1): 
            if j != rows: 
                print('*', end = '') 
        print() 
    print() 
  
# Driver Code 
  
# Get N 
N = 6
  
# Print the pattern  
pattern(N) 
  
# This code is contributed by  
# SamyuktaSHegde  
 
  

C#

   // C# program for printing 
// the hollow triangle pattern 
using System; 
  
class GFG 
{ 
  
// Function for printing pattern 
static void pattern(int N) 
{ 
    int i, j, k = 0, space = 1, rows = N; 
  
    // For printing stars 
    for (i = rows; i >= 1; i--)  
    { 
        for (j = 1; j <= i; j++)  
        { 
            Console.WriteLine("*"); 
        } 
        if (i != rows)  
        { 
            // for printing space 
            for (k = 1; k <= space; k++) 
            { 
            Console.Write(" "); 
            } 
  
            // increment by 2 
            space = space + 2; 
        } 
        for (j = i; j >= 1; j--)  
        { 
            if (j != rows) 
                Console.Write("*"); 
        } 
        Console.Write("\n"); 
    } 
    Console.Write("\n"); 
} 
  
// Driver code 
public static void Main() 
{ 
  
    // Get N 
    int N = 6; 
  
    // Print the pattern 
    pattern(N); 
}  
} 
  
// This code is contributed  
// by Rajput-Ji 
 
  

PHP

   <?php 
// PHP program for printing 
// the hollow triangle pattern 
  
// Function for printing pattern 
function pattern($N) 
{ 
    $k = 0; 
    $space = 1; 
    $rows = $N; 
  
    // For printing stars 
    for ($i = $rows; $i >= 1; $i--)  
    { 
        for ($j = 1; $j <= $i; $j++)  
        { 
            echo "*"; 
        } 
        if ($i != $rows)  
        { 
            // for printing space 
            for ($k = 1; $k <= $space; $k++) 
            { 
                echo " "; 
            } 
  
            // increment by 2 
            $space = $space + 2; 
        } 
        for ($j = $i; $j >= 1; $j--) 
        { 
            if ($j != $rows) 
                echo "*"; 
        } 
        echo "\n"; 
    } 
    echo "\n"; 
} 
  
// Driver code 
  
// Get N 
$N = 6; 
  
// Print the pattern 
pattern($N); 
  
// This code is contributed by 
// Archana_kumari  
?> 
 
  

Javascript

   <script> 
      // JavaScript program for printing 
      // the hollow triangle pattern 
  
      // Function for printing pattern 
      function pattern(N) { 
        var i, 
          j, 
          k = 0, 
          space = 1, 
          rows = N; 
  
        // For printing stars 
        for (i = rows; i >= 1; i--) { 
          for (j = 1; j <= i; j++) { 
            document.write("*"); 
          } 
          if (i != rows) { 
            // for printing space 
            for (k = 1; k <= space; k++) { 
              document.write("  "); 
            } 
  
            // increment by 2 
            space = space + 2; 
          } 
          for (j = i; j >= 1; j--) { 
            if (j != rows) document.write("*"); 
          } 
          document.write("<br>"); 
        } 
        document.write("<br>"); 
      } 
  
      // Driver code 
      // Get N 
      var N = 6; 
        
      // Print the pattern 
      pattern(N); 
        
      // This code is contributed by rdtank. 
    </script>
 
  

Output:

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

Time complexity: O(n²)

Auxiliary Space: O(1)

C++ Program To Print Triangle Pattern

Kanishk_Verma

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Article Tags :

Practice Tags :

pattern-printing

Program to print hollow Triangle pattern

C++

C

Java

Python3

C#

PHP

Javascript

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