Swift Program to Print Half Diamond Star Pattern

This tutorial will discuss how to write swift program to print half diamond star pattern.

Star pattern is a sequence of "*" which is used to develop different patterns or shapes like pyramid, rectangle, cross, etc. These star patterns are generally used to understand or practice the program flow controls, also they are good for logical thinking.

Create a half diamond star pattern, we can use any of the following methods ?

• Using nested for loop

• Using init() Function

• Using stride Function

Below is a demonstration of the same ?

Input

Suppose our given input is ?

Num = 7

Output

The desired output would be ?

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

Method 1 - Using Nested For Loop

We can create a half diamond star pattern or any other pattern using nested for loops. Here each for loop handle different tasks such as outermost for loop is used for new rows, and nested for loop is used for "*".

Algorithm

Following is the algorithm ?

Step 1 ? Declare variable to store the height of the half diamond star pattern

For upper half diamond star pattern ?

Step 2 ? Run an outer for loop from 1 to num. This loop handle the total number of rows are going to print and each row is start with new line.

Step 3 ? Run nested for loop from 1 to i. This loop is used print upper half diamond star pattern.

For lower half diamond star pattern ?

Step 4 ? Again run an outer for loop from 1 to num-1. This loop handle the total number of rows are going to print and each row is start with new line.

Step 5 ? Run another nested for loop from 1 to num-j. This loop is used print lower half diamond star pattern.

Example

The following program shows how to print half diamond star pattern using nested for loop.

<div class="execute"></div><div class="code-mirror  language-javascript" contenteditable="plaintext-only" spellcheck="false" style="outline: none; overflow-wrap: break-word; overflow-y: auto; white-space: pre-wrap;"><span class="token keyword">import</span> Foundation
<span class="token keyword">import</span> Glibc

<span class="token comment">// Height of the half diamond star pattern</span>
<span class="token keyword">let</span> num <span class="token operator">=</span> <span class="token number">9</span>

<span class="token comment">// Outer for loop is used to handle the</span>
<span class="token comment">// total number of rows in upper half</span>
<span class="token comment">// diamond star pattern</span>
<span class="token keyword">for</span> i <span class="token keyword">in</span> <span class="token number">1.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>num<span class="token punctuation">{</span>

   <span class="token comment">// Nested for loop is used to print</span>
   <span class="token comment">// upper half diamond star pattern</span>
   <span class="token keyword">for</span> _ <span class="token keyword">in</span> <span class="token number">1.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>i<span class="token punctuation">{</span>
      <span class="token function">print</span><span class="token punctuation">(</span><span class="token string">"*"</span><span class="token punctuation">,</span> terminator<span class="token operator">:</span> <span class="token string">""</span><span class="token punctuation">)</span>
   <span class="token punctuation">}</span>
   
   <span class="token comment">// Add new line</span>
   <span class="token function">print</span><span class="token punctuation">(</span><span class="token string">""</span><span class="token punctuation">)</span>
<span class="token punctuation">}</span>

<span class="token comment">// Outer for loop is used to handle the</span>
<span class="token comment">// total number of rows in lower half</span>
<span class="token comment">// diamond star pattern</span>
<span class="token keyword">for</span> j <span class="token keyword">in</span> <span class="token number">1.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>num<span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">{</span>

   <span class="token comment">// Nested for loop is used to print</span>
   <span class="token comment">// lower half diamond star pattern</span>
   <span class="token keyword">for</span> _ <span class="token keyword">in</span> <span class="token number">1.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>num<span class="token operator">-</span>j<span class="token punctuation">{</span>
      <span class="token function">print</span><span class="token punctuation">(</span><span class="token string">"*"</span><span class="token punctuation">,</span> terminator<span class="token operator">:</span> <span class="token string">""</span><span class="token punctuation">)</span>
   <span class="token punctuation">}</span>
   
   <span class="token comment">// Add new line</span>
   <span class="token function">print</span><span class="token punctuation">(</span><span class="token string">""</span><span class="token punctuation">)</span>
<span class="token punctuation">}</span>
</div><div class="output-wrapper"><div class="console-close"></div><div class="code-output"></div></div>

Output

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

Method 2 - Using init() Function

Swift provide an in-built function named String.init(). Using this function, we can able to create any pattern. String.init() function create a string in which the given character is repeated the specified number of times.

Syntax

Following is the syntax ?

String.init(repeating:Character, count: Int)

Here, repeating represent the character which this method repeats and count represent the total number of time the given character repeat in the resultant string.

Algorithm

Following is the algorithm ?

Step 1 ? Declare variable to store the length of the half diamond star pattern.

Step 2 ? Run a for loop from 1 to num. This loop prints the upper hand diamond star pattern using init() function ?

for x in 1...num{
   print(String.init(repeating: "*", count: x))
}

Here, in each iteration init() function print "*" according to the value of x. For example if x = 2, then init() prints "**".

Step 3 ? Run another for loop from 1 to num-1. This loop prints the lower half diamond star pattern using init() function ?

for x in 1...num-1{
   print(String.init(repeating: "*", count: num-x))
}

Example

The following program shows how to print half diamond star pattern using string.init() function.

<div class="execute"></div><div class="code-mirror  language-javascript" contenteditable="plaintext-only" spellcheck="false" style="outline: none; overflow-wrap: break-word; overflow-y: auto; white-space: pre-wrap;"><span class="token keyword">import</span> Foundation
<span class="token keyword">import</span> Glibc

<span class="token comment">// Height of the half diamond star pattern</span>
<span class="token keyword">let</span> num <span class="token operator">=</span> <span class="token number">9</span>

<span class="token comment">// Creating upper half diamond star pattern</span>
<span class="token comment">// Using String.init() function</span>
<span class="token keyword">for</span> x <span class="token keyword">in</span> <span class="token number">1.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>num<span class="token punctuation">{</span>
   <span class="token function">print</span><span class="token punctuation">(</span>String<span class="token punctuation">.</span><span class="token function">init</span><span class="token punctuation">(</span>repeating<span class="token operator">:</span> <span class="token string">"*"</span><span class="token punctuation">,</span> count<span class="token operator">:</span> x<span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token punctuation">}</span>

<span class="token comment">// Creating lower half diamond star pattern</span>
<span class="token comment">// Using String.init() function</span>
<span class="token keyword">for</span> x <span class="token keyword">in</span> <span class="token number">1.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>num<span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">{</span>
   <span class="token function">print</span><span class="token punctuation">(</span> String<span class="token punctuation">.</span><span class="token function">init</span><span class="token punctuation">(</span>repeating<span class="token operator">:</span> <span class="token string">"*"</span><span class="token punctuation">,</span> count<span class="token operator">:</span> num<span class="token operator">-</span>x<span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token punctuation">}</span>
</div><div class="output-wrapper"><div class="console-close"></div><div class="code-output"></div></div>

Output

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

Method 3 - Using Stride Function

Swift provide an in-built function named stride(). The stride() function is used to move from one value to another with increment or decrement. Or we can say stride() function return a sequence from the starting value but not include end value and each value in the given sequence is steps by the given amount.

Syntax

Following is the syntax ?

stride(from:startValue, to: endValue, by:count)

Here,

from ? Represent the starting value to used for the given sequence.

to ? Represent the end value to limit the given sequence

by ? Represent the amount to step by with each iteration, here positive value represent upward iteration or increment and negative value represent the downward iteration or decrement.

Example

The following program shows how to print half diamond star pattern using stride() function.

<div class="execute"></div><div class="code-mirror  language-javascript" contenteditable="plaintext-only" spellcheck="false" style="outline: none; overflow-wrap: break-word; overflow-y: auto; white-space: pre-wrap;"><span class="token keyword">import</span> Foundation
<span class="token keyword">import</span> Glibc
<span class="token comment">// Height of the half diamond star pattern</span>
<span class="token keyword">let</span> num <span class="token operator">=</span> <span class="token number">9</span>
<span class="token comment">// For upper half diamond star pattern</span>
<span class="token keyword">for</span> i <span class="token keyword">in</span> <span class="token number">1.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>num<span class="token punctuation">{</span>
   <span class="token comment">// Printing upper half diamond star pattern</span>
   <span class="token keyword">for</span> _ <span class="token keyword">in</span> <span class="token number">1.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>i<span class="token punctuation">{</span>
      <span class="token function">print</span><span class="token punctuation">(</span><span class="token string">"*"</span><span class="token punctuation">,</span> terminator <span class="token operator">:</span> <span class="token string">""</span><span class="token punctuation">)</span>
   <span class="token punctuation">}</span>
   <span class="token comment">// Adding new line</span>
   <span class="token function">print</span><span class="token punctuation">(</span><span class="token string">" "</span><span class="token punctuation">)</span>
<span class="token punctuation">}</span>
<span class="token comment">// For lower half diamond star pattern</span>
<span class="token keyword">for</span> j <span class="token keyword">in</span> <span class="token number">1.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>num<span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">{</span>
   <span class="token comment">// Printing lower half diamond star pattern</span>
   <span class="token keyword">for</span> _ <span class="token keyword">in</span> <span class="token function">stride</span><span class="token punctuation">(</span><span class="token parameter">from<span class="token operator">:</span> num<span class="token punctuation">,</span> to<span class="token operator">:</span> j<span class="token punctuation">,</span> by<span class="token operator">:</span> <span class="token operator">-</span><span class="token number">1</span></span><span class="token punctuation">)</span><span class="token punctuation">{</span>
      <span class="token function">print</span><span class="token punctuation">(</span><span class="token string">"*"</span><span class="token punctuation">,</span> terminator <span class="token operator">:</span> <span class="token string">""</span><span class="token punctuation">)</span>
   <span class="token punctuation">}</span>
   <span class="token comment">// Adding new line</span>
   <span class="token function">print</span><span class="token punctuation">(</span><span class="token string">" "</span><span class="token punctuation">)</span>
<span class="token punctuation">}</span>
</div><div class="output-wrapper"><div class="console-close"></div><div class="code-output"></div></div>

Output

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