 # C++ Program to print diamond pattern of stars

July 23, 2021, Learn eTutorial
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Here is a C++ program to print diamond patterns.

## How to make a diamond pattern?

Generally, to print a diamond pattern, we need to print two triangles. One in an upward direction and one in reverse, simply print the first triangle and the second triangle in reverse of the first triangle.

## print diamond pattern of stars in C++

To print a diamond pattern of stars in C++ programming, ask the user to enter the number of rows.

If the user enters  8 as the row size of the diamond, then its upper-triangular part expands up to 8 lines, whereas its lower-triangular part expands up to 7 (one less than row size) lines.

Get the entered number into a variable rownum. Set another variable space to rownum-1.
We are using three` for loops` to create each triangle, the upper triangle and the lower triangle of the diamond.

• 1 corresponds to rows
• 2 corresponds to spaces
• 3 corresponds to columns.

Consider an example of 8.
rownum = 8; space = 7;

The `for loop` started execution i =0  and condition i <= 8 evaluates to be true.

`for(i=1; i<=rowNum; i++)`

control flow goes inside the loop, now j = 1 and condition j <= 7 evaluates to be true.

`for(j=1; j<=space; j++)`

inside the loop prints a single space.
`cout<<" ";`

everytime after exiting from this loop, decrement the value of space to print one less space from next line or row.
`space--;`

Use the third `for loop` to print stars. At first execution, j=1 and the condition j<=(2*i-1) or j<=(2*1-1) or 1<=(1) or 1<=1 evaluates to be true, therefore program flow goes inside this loop and prints a star (*).

```for(j=1; j<=(2*i-1); j++)    cout<<"*";```

Using `endl`, the next thing starts from the new line.

`cout<;`

this process continues until the condition evaluates to be false.

In this way, the star pattern of the upper diamond gets printed, similarly, the lower diamond also gets printed.

### Algorithm

Step 1: Call the header file iostream.

Step 2: Use the namespace std.

Step 3: Open the integer type main function; int main().

Step 4: Declare  integer type variables rownum, space, I, j;

Step 5: Ask the user to enter the number of rows.

Step 6: Get the number into the variable rownum;

Step 7: Set the value of the variable space to rownum – 1;

Step 8: create a for loop corresponding to rows. Initialize the value of i to 0; Check for the condition i <= rownum. go to step 9 for true;

Step 9:  Create a for loop that corresponds to the spaces

• Initialize j = 1 and check for the condition j <= space
• Print a space for true and decrement the value of space by 1 after each  iteration.
• Also, increment the value of j by 1

Step 10: Create another for loop that corresponds to the printing of stars
With j= 1 at first execution and check for the condition  j<=(2*i-1) or j<=(2*1-1)  or 1<=(1) or 1<=1. Print a star for true;
Increment the value of j by 1;

Step 11:set space =1;

Step 12: Repeat steps 8, 9, and 10;

Step 13: Exit.

## C++ Source Code

```                                          ```#include<iostream>
using namespace std;
int main()
{
int i, j, rownum, space;
cout<<"Enter the Number of Rows: ";
cin>>rownum;
space = rownum-1;
for(i=1; i<=rownum; i++)
{
for(j=1; j<=space; j++)
cout<<" ";
space--;
for(j=1; j<=(2*i-1); j++)
cout<<"*";
cout<<endl;
}
space = 1;
for(i=1; i<=(rownum-1); i++)
{
for(j=1; j<=space; j++)
cout<<" ";
space++;
for(j=1; j<=(2*(rownum-i)-1); j++)
cout<<"*";
cout<<endl;
}
cout<<endl;
return 0;
}```
```

## OUTPUT

```Enter the Number of Rows: 8
*
***
*****
*******
*********
***********
*************
***************
*************
***********
*********
*******
*****
***
*
```