Pattern Programming in C++

Introduction

Pattern programming means printing different patterns, such as triangles, pyramids, rectangles, etc., using a programming language.

Pattern programming in C++ requires a decent knowledge of loops or, more specifically, nested loops. Writing code(s) to print patterns using special characters, numbers, and alphabets makes one understand how the loops work internally.

• In this article, the code to print triangles, pyramids, and rectangles using *, numbers, and alphabets has been shown.
• Other complex patterns, like the Butterfly diagram and Pascal's triangle, have also been shown.

Top C++ Pattern Programs:

• Print triangles using *, numbers, and characters
• Rectangle Pattern
• Hollow Rectangle Pattern
• Inverted Half Pyramid
• Floyd’s Triangle
• Butterfly Pattern
• Print Pascal's triangle
• Print Full Pyramid Pattern of Stars
• Print Pattern of Stars
• C++ Print Triangle Star Pattern
• C++ Print Pattern of Numbers

C++ Programs for Important Patterns

Print triangle using "*", numbers, and characters

To print a triangle pattern program in C++, we will use two nested loops with iterable variables as i and j. The whole logic to print a triangle using x is as follows, where x can be *, number, and character:

• Take input from the user of the number of rows in the triangle. Let it be rows.
• Iterate for $i=0$ to $i=rows-1$ and do :
  • Iterate for $j=0$ to $j=rows$ and print $x$ + space each time i.e cout << x << " ";
  • Terminate the current line, i.e. cout << endl;

When we implement the above logic, the inner loop will print x 1 time in the first row, then two times in the second row, and so on.

Code 1: Printing half pyramid using *

To print a half pyramid/triangle using *, we will replace the $x$ with *, and we are good to go.

Source Code:

Output:

Code 2: Printing half pyramid using numbers

Again to print a pyramid of numbers, we need to replace $x$ with $i+1$, where $i+1$ denotes the row number. Here it is $i+1$ because we are starting $i$ from 0.

Source Code:

Output:

Code 3: Printing half pyramid using Alphabets

Similarly, we will replace the $x$ with the desired alphabets to print a pyramid of alphabets.

Source Code:

Output:

Rectangle pattern

Coding a rectangle pattern program in C++ is similar to printing a matrix of dimensions $n\times m$.

The logic is as follows :

• Take the input of rows and columns (dimensions) of the rectangle. Let them be rows and cols.
• Iterate from $i=0$ to $i=rows$ and do the following :
  • Iterate from $j=0$ to $j=cols$ and print $x$ + space each time $i.e$ cout << x << " ";
  • Terminate the current line, $i.e.$ cout << endl;

Source Code:

Output :

Hollow Rectangle Pattern

The process to code the hollow rectangle pattern program in C++ is almost the same as printing a normal rectangle with the only difference that while printing a hollow rectangle, we need to take care of printing empty spaces for non-border cells.

The logic is as follows :

• Take the input of rows and columns (dimensions) of the rectangle. Let them be rows and cols.
• Iterate from $i=0$ to $i=rows$ and do the following :
  • Iterate from $j=0$ to $j=cols$ and do the following :
    • If current is the border cell of rectangle $i.e.$ i = 0 OR i = rows - 1 OR j = 0 OR j = cols - 1 print * + space.
    • Otherwise, print blank space.

Source Code:

Output:

Floyd's triangle

In Floyd's triangle, we need to print numbers, but it is also required to increase the number by 1 each time we print it. Floyd's Triangle is similar to the half triangle using numbers, with the only difference being that in Floyd's triangle, we need to maintain a counter which will be incremented by one each time it is printed. The logic is as follows :

• Take input from the user of the number of rows in the triangle. Let it be $rows$.
• Define a variable, say $counter$ and initialize its value to 0.
• Iterate for $i=0$ to $i=rows-1$ and do :
  • Iterate for $j=0$ to $j=rows$ and do the following :
    • Print $count$ + space each time $i.e$ cout << count << " ";
    • Increase the value of count by 1 $i.e.$ count++.
  • Terminate the current line, $i.e.$ cout << endl;

Source Code:

Output:

Butterfly Pattern

To easily print the butterfly pattern in C++, we will split our code into two parts, i.e., print the upper part in the first go and then the second part.

The logic is as follows :

• Take input from the user of the number of rows in the Butterfly pattern. Let it be $rows$.
• Iterate from $i=0$ to $i=rows-1$ and do the following -
  • Iterate from $j=0$ to $j = i$ and print *+ Blank space $i.e.$ cout << "*" << " ";
  • Define a variable to find the number of spaces needed to be printed; say it to be $space$.
  • Initialize its value to be $2\times (rows - i)$.
  • Iterate from $j=0$ to $j=spaces-1$ and print blank spaces.
  • Iterate from $j=0$ to $j = i$ and print *+ Blank space $i.e.$ cout << "*" << " ";
  • Terminate the line, $i.e.$ count << endl;
• Repeat the above-given steps, but this time Iterate from $i=rows - 1$ to $i=0$. This will print the lower part, as we have already printed the upper part.

Source Code :

Output:

Print Pascal's triangle

Pascal's triangle is a triangle that consists of a binomial coefficient $i.e.$ $\binom{n}{r}$ (number of ways to choose $r$ things elements a set of $n$ elements). We can easily find the value of $\binom{n}{r}$ using pascal's triangle by looking at the $r^{th}$ value in the $n^{th}$ row.

The logic for printing pascal's triangle is as follows :

• Take input from the user of the number of rows in the triangle. Let it be $rows$.
• Iterate from $i=0$ to $i=rows-1$ and do the following :
  • Print $rows - i$ spaces using a for a loop.
  • Define a variable, say coefficient.
  • Iterate from $j=0$ to $j=i$ and do the following :
    • If $j==0$, then set coefficient's value to be 1.
    • Otherwise multiply (i - j + 1) to coefficient and divide it by j $i.e.$ coefficient * = (i - j + 1) / j;
    • Print coefficient + space i.e. cout << coefficient << " ";
  • Terminate the line $i.e.$ cout << endl;

Source Code:

Output:

Print Full Pyramid Pattern of Stars

Printing the full pyramid is almost the same as printing the half pyramid. We need to print space before printing the *s. The logic is as follows :

• Take input from the user of the number of rows in the triangle. Let it be $rows$.
• Iterate from $i=0$ to $i=rows - 1$ and do the following :
  • Define a variable to find the number of spaces needed to be printed. Say it to be $space$.
  • Initialize its value to be $rows - i$.
  • Iterate from $j=0$ to $j=space - 1$ and print double spaces.
  • Iterate from $j=0$ to $j=2\times i - 1$ and print *+space.
  • Terminate the line i.e. cout << endl;

Source Code:

Output:

Print pattern of Stars.

The following code contains some of the pattern programs in c++ combined, which we have already seen in the previous sections of this article.

Source Code:

Output:

C++ Print Triangle Star Pattern

1. Simple triangle.

Code

Output

2. Inverted triangle.

Code

Output

C++ Print Pattern of Numbers

Code

Output