Program to print Square inside a Square

Given a number N, print a hollow square of side with N asterisks(‘*’), and inside it print a hollow square of side N-4 asterisks(‘*’).
Examples :

Input : 6
Output :
******
*    *
* ** *
* ** *
*    *
******

Input :9
Output :
*********
*       *
* ***** *
* *   * *
* *   * *
* *   * *
* ***** *
*       *
*********

The idea is to run two nested loops from 1 to n for rows and columns and now to check for conditions when to print an asterisk(‘*’) and when to print space(‘ ‘). The condition for printing asterisks will be: 

// This will print asterisks on the boundary
(i == 1 || i == n || j == 1 || j == n)

// This will print the asterisks on the boundary
// of inner square
(i >= 3 && i = 3 && j <= n - 2) &&
(i == 3 || i == n - 2 || j == 3 || j == n - 2))

All of the indexes which do not satisfy the above condition will contain space.
Below is the implementation of above idea: 

C++

// C++ program to print square inside
// a square pattern
#include <iostream>
using namespace std;


// Function to print the pattern square
// inside a square
void printPattern(int n)
{
    int i, j;

    // To access rows of the square
    for (i = 1; i <= n; i++)
    {
        // To access columns of the square
        for (j = 1; j <= n; j++)
        {

            // For printing the required square pattern
            if ((i == 1 || i == n || j == 1 || j == n) ||
                (i >= 3 && i <= n - 2 && j >= 3 && j <= n - 2) &&
                 (i == 3 || i == n - 2 || j == 3 || j == n - 2))
            {
                // Prints star(*)
                cout<<"*";
            }
            else
            {
                // Prints space(" ")
                cout<<" ";
            }
        }

        cout<<endl;
    }
}

// Driver Code
int main()
{
    int n = 7;
    printPattern(n);
    return 0;
}

// This code is contributed by Shivam.Pradhan.

C

// C program to print square inside
// a square pattern
#include <stdio.h>

// Function to print the pattern square
// inside a square
void printPattern(int n)
{
    int i, j;

    // To access rows of the square
    for (i = 1; i <= n; i++)
    {
        // To access columns of the square
        for (j = 1; j <= n; j++)
        {

            // For printing the required square pattern
            if ((i == 1 || i == n || j == 1 || j == n) ||
                (i >= 3 && i <= n - 2 && j >= 3 && j <= n - 2) &&
                 (i == 3 || i == n - 2 || j == 3 || j == n - 2))
            {
                // Prints star(*)
                printf("*");
            }
            else
            {
                // Prints space(" ")
                printf(" ");
            }
        }

        printf("\n");
    }
}

// Driver Code
int main()
{
    int n = 7;
    printPattern(n);
    return 0;
}

Java

// Java program to print square inside
// a square pattern
import java.lang.*;

class GFG {

// Function to print the pattern square
// inside a square
static void printPattern(int n) {

    // To access rows of the square
    for (int i = 1; i <= n; i++) {

    // To access columns of the square
    for (int j = 1; j <= n; j++) {

        /*** For printing the required square pattern ***/
        if ((i == 1 || i == n || j == 1 || j == n) ||
            (i >= 3 && i <= n - 2 && j >= 3 && j <= n - 2) &&
                (i == 3 || i == n - 2 || j == 3 || j == n - 2))
        {
        // Prints star(*)
        System.out.print("*");
        }
        else
        {
        // Prints space(" ")
        System.out.print(" ");
        }
    }

    System.out.print("\n");
    }
}

// Driver code
public static void main(String[] args) {
    int n = 7;
    printPattern(n);
}
}

// This code is contributed by Anant Agarwal.

Python3

# Python program to
# print square inside
# a square pattern

# Function to print
# the pattern square
# inside a square
def printPattern(n):

    # To access rows of the square
    for i in range(1,n+1):

        # To access columns of the square
        for j in range(1,n+1):

            # For printing the required square pattern
            if ((i == 1 or i == n or j == 1 or j == n) or
                (i >= 3 and i <= n - 2 and j >= 3 and j <= n - 2) and
                    (i == 3 or i == n - 2 or j == 3 or j == n - 2)):

                print("*",end="") # Prints star(*)

            else:

                print(" ",end="") # Prints space(" ")

        print()


# Driver code

n = 7
printPattern(n)

# This code is contributed
# by Anant Agarwal.

C#

// C# program to print square inside
// a square pattern
using System;

class GFG {

    // Function to print the pattern square
    // inside a square
    static void printPattern(int n) {

        // To access rows of the square
        for (int i = 1; i <= n; i++) {

            // To access columns of the square
            for (int j = 1; j <= n; j++) {

                /*** For printing the required
                     square pattern ***/
                if ((i == 1 || i == n || j == 1
                       || j == n) || (i >= 3 &&
                        i <= n - 2 && j >= 3 &&
                      j <= n - 2) && (i == 3 ||
                        i == n - 2 || j == 3 ||
                                   j == n - 2))
                {

                    // Prints star(*)
                    Console.Write("*");
                }
                else
                {

                    // Prints space(" ")
                    Console.Write(" ");
                }
            }

            Console.WriteLine();
        }
    }

    // Driver code
    public static void Main() {

        int n = 7;

        printPattern(n);
    }
}

// This code is contributed by vt_m.

PHP

<?php
// PHP program to print square inside
// a square pattern

// Function to print the pattern square
// inside a square
function printPattern($n)
{
    // To access rows of the square
    for ($i = 1; $i <= $n; $i++)
    {
        // To access columns of the square
        for ($j = 1; $j <= $n; $j++)
        {

            // For printing the required
            // square pattern
            if (($i == 1 || $i == $n ||
                $j == 1 || $j == $n) ||
                ($i >= 3 && $i <= $n - 2 &&
                $j >= 3 && $j <= $n - 2) &&
                ($i == 3 || $i == $n - 2 ||
                $j == 3 || $j == $n - 2))
            {
                // Prints star(*)
                echo "*";
            }
            else
            {
                // Prints space " "
                echo " ";
            }
        }

        echo"\n";
    }
}

// Driver Code
$n = 7;
printPattern($n);

// This code is contributed by Mithun Kumar
?>

Javascript

// JavaScript program to print square inside
// a square pattern

function printPattern(n) {
// To access rows of the square
for (let i = 1; i <= n; i++) {

    // To access columns of the square
    for (let j = 1; j <= n; j++) {

        /*** For printing the required square pattern ***/
        if ((i == 1 || i == n || j == 1 || j == n) ||
            (i >= 3 && i <= n - 2 && j >= 3 && j <= n - 2) &&
            (i == 3 || i == n - 2 || j == 3 || j == n - 2))
        {
            // Prints star(*)
            process.stdout.write("*");
        }
        else
        {
            // Prints space(" ")
            process.stdout.write(" ");
        }
    }

    process.stdout.write("\n");
}
}

// Driver code
let n = 7;
printPattern(n);

Output :

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

Time Complexity: O(n²)
Auxiliary Space: O(1)