# Diamond Pattern in C++ using For Loop

### For Loop:

A for loop is a repetitive control structure that allows you to create a loop for executing a specific number of times.

The syntax of for loop:

In C++, a for loop is written as

``````for ( initialize; condition; incrementation )
{
statement(x);
}
``````

Before we move on the diamond star pattern, first we have to know the code of star pyramid and inverted star pyramid.

### 1. Right Triangle Star Pyramid:

Algorithm:

1. Assume that the number of rows in a right triangle is n.
2. In the Nth row, the number of stars is always K. The first row has one star, the second row has two stars, and the third row has three stars. The Kth row, on average, has K stars.
3. To print the proper triangle star design, we'll utilize two loops.
• The outer for loop will iterate n times for a right triangular star design with "n" rows. The pattern will be printed one row at a time in each outer loop iteration.
• The inner loop will also run n times for the Nth row of the right triangle pattern. One star (*) will be printed for each inner loop iteration.

In the code, programmer/user enters the number of rows he wants display the stars on the screen.

Program in C++ to print right triangle star pyramid pattern

``````#include <iostream>
using namespace std;
int main()
{
int  i, j, n;
cout << "Enter number of rows:  ";
cin >> n;
for(i = 1; i <= n; i++)     // outer loop(to print rows)
{
for(j = 1; j <= i; j++)      //inner loop(to print columns)
{
cout << "* ";
}
//Ending line after each row //
cout << "\n";
}
return 0;
}
``````

Output:

``````*
*  *
*  *  *
*  *  *  *
``````

### 2. Inverted right triangle star pyramid

Algorithm:

The right triangular star pattern is inverted vertically in this algorithm. As the row number goes from top to bottom, so the number of stars in a row reduces.

NOTE: The row and column indexes always start at 0.

1. Take the inverted right triangle's number of rows (n) as input. In an inverted right triangle (n - k + 1) is the number of stars in the kth row. Let, n be 4 in the pattern. As a result, the first row has four stars, the second row has three stars, the third row has two stars, and the fourth row has only one star.
2. To print an inverted right triangular star design, we'll use two for loops.
• The outer for loop will iterate n times (from I = 0 to n-1) for an inverted right triangular star design with M rows. The code will be printed one row at a time in each iteration of this loop.
•  The inner loop will iterate M-j times (from j = 0 to n-j) for the jth row of the inverted right triangle pattern. The inner loop will print one star character for each iteration.

Program to print Inverted right triangle star pyramid pattern

``````#include <iostream>
using namespace std;
int main()
{
int  i, j, n;
cout << "Enter the number of rows:  ";
cin >> n;
for(i = n; i >= 1; i--)
{
for(j = 1; j <= i; j++)
{
cout << "* ";
}
// ending line after each row
cout << "\n";
}
return 0;
}
``````

Output:

``````*  *  *  *
*  *  *
*  *
*``````

### Pyramid star pattern:

Algorithm:

In this program, we print a pyramid star pattern with (2*i + 1) space-separated stars in the ith row.

The row and column indexes begin at 0.

The number of rows (N) in the pattern is the input taken by the user.

The outer loop will print a row of the pyramid (from I = 0 to N - 1) after one iteration.

The inner for loop prints (N - i - 1) spaces for every line in the jth row of the pyramid, then nested while the loop prints (2*j + 1) stars.

Program in C++ to print star pyramid pattern:

``````#include<iostream>
using namespace std;
int main()
{
int n, s, i, j;
cout << "Enter number of rows: ";
cin >> n;
for(i = 1; i <= n; i++)
{
//for loop for displaying space
for(s = i; s < n; s++)
{
cout << " ";
}
//for loop to display star equal to the row number
for(j = 1; j <= (2 * i - 1); j++)
{
cout << "*";
}
// ending line after each row
cout << "\n";
}
}
``````

Output:

``````Enter the number of rows: 4
*
* * *
* * * * *
* * * * * * *
``````

### Inverted star pyramid:

Algorithm:

In this algorithm, the rows are printed in reverse order, which is comparable to the pyramid star pattern.

1. The number of rows (n) in the pattern is the first input.
2. a) In one iteration, the outer for loop (from I = 0 to n-1) will print a row of inverted pyramids.
b) The inner for loops print "S" spaces followed by (2*(n-i) - 1) star character in the jth row.

Program in C++ to print inverted star pyramid pattern:

``````#include<iostream>
using namespace std;
int main()
{
int n, s, i, j;
cout << "Enter number of rows: ";
cin >> n;
for( i=n; i>= 1; i-- )
{
//for loop to put space
for(s = i; s < n; s++)
{
cout << " ";
}
//for loop for displaying star
for(j = 1; j <= i; j++)
{
cout << "* ";
}
// ending line after each row
cout << "\n";
}
return 0;
}
``````

Output:

``````Enter number of rows: 4
*  *  * *
* *  *
* *
*
``````

### Diamond star pattern:

The diamond star pattern is the combination of the pyramid and inverted pyramid pattern. The following c++ program combines the code of simple pyramid and the code of reverse pyramid star.

Program to print full star diamond pattern in C++:

``````#include<iostream>
using namespace std;
int main()
{
int n, s, i, j;
cout << "Enter number of rows: ";
cin >> n;
//loop to print the upper diamond pattern //
for(i = 0; i <= n; i++)
{
for(s = n; s > i; s--)
cout << " ";
for(j=0; j<i; j++)
cout << "* ";
cout << "\n";
}
// for loop to print the inverted diamond pattern //
for(i = 1; i < n; i++)
{
for(s = 0; s < i; s++)
cout << " ";
for(j = n; j > i; j--)
cout << "* ";
// ending line after each row
cout << "\n";
}
return 0;
}
``````

Output:

``````              *
*   *
*    *    *
*    *    *    *
*    *     *
*     *
* ``````