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Program to print hollow Triangle pattern

  • Last Updated : 06 Apr, 2021

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

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

Approach:
 

  1. Input number of rows to print from the user as N.
  2. 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–).
  3. 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.
  4. 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: 
***********
***** *****
****   ****
***     ***
**       **
*         *

 

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