C++ || Printing Various Patterns Using Nested Loops
This page will demonstrate various programs which illustrates the use of nested loops to print selected patterns to the screen.
REQUIRED KNOWLEDGE FOR THIS PAGE
The following are famous homework assignments which are usually presented in an entry level programming course.
There are a total of ten (10) different patterns on this page, which is broken up into sections. This page will list:
(4) methods of printing a triangle
(4) methods of printing an upside down triangle
(1) method which prints a square
(1) method which prints a giant letter 'X'
======= PRINTING A TRIANGLE =======
This program prints a triangle shape to the screen.
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#include <iostream> using namespace std; int main() { // declare variables int number=0; int counter=1; // get data from user cout<<"Enter a number: "; cin>>number; // this is the start of the nested loop. // NOTE: many use two nested 'for' loops, but // sometimes its nice to switch things up while(counter <= number) { for(int x=0; x < counter; ++x) { cout<<"* "; } cout<<endl; ++counter; } return 0; }// http://programmingnotes.org/ |
In the above example, the user has a choice of entering the number of rows which will be displayed to the screen
SAMPLE OUTPUT:
Enter a number: 9
*
* *
* * *
* * * *
* * * * *
* * * * * *
* * * * * * *
* * * * * * * *
* * * * * * * * *
======= PRINTING A TRIANGLE WITH NUMBERS =======
The following program uses the same concept as above, but this time instead of using stars “*”, numbers will be printed to the screen.
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#include <iostream> using namespace std; int main() { // declare variables int number=0; int counter=1; int copy=0; // get data from user cout<<"Enter a number: "; cin>>number; // this variable is just a copy // of the number that the user just entered // which will be used in the nested loop copy=number; // this is the start of the nested loop. // NOTE: many use two nested 'for' loops, but // sometimes its nice to switch things up while(counter <= number) { for(int x=0; x < counter; ++x) { cout<<copy<<" "; } cout<<endl; --copy; ++counter; } return 0; }// http://programmingnotes.org/ |
SAMPLE OUTPUT:
Enter a number: 9
9
8 8
7 7 7
6 6 6 6
5 5 5 5 5
4 4 4 4 4 4
3 3 3 3 3 3 3
2 2 2 2 2 2 2 2
1 1 1 1 1 1 1 1 1
======= PRINTING A TRIANGLE WITH NUMBERS IN-ORDER =======
The following program uses the same concept as above, but this time instead of using stars “*”, numbers will be printed to the screen in-order.
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#include <iostream> using namespace std; int main() { // declare variables int number=0; int counter=1; int copy=0; // get data from user cout<<"Enter a number: "; cin>>number; // this is the start of the nested loop. // NOTE: many use two nested 'for' loops, but // sometimes its nice to switch things up while(counter <= number) { copy=number; for(int x=0; x < counter; ++x) { cout<<copy-(counter-1)<<" "; ++copy; } cout<<endl; ++counter; } return 0; }// http://programmingnotes.org/ |
SAMPLE OUTPUT:
Enter a number: 9
9
8 9
7 8 9
6 7 8 9
5 6 7 8 9
4 5 6 7 8 9
3 4 5 6 7 8 9
2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
======= PRINTING A TRIANGLE WITH NUMBERS USING MULTIPLICATION =======
This example demonstrates another triangle, this time printing a multiplication table.
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#include <iostream> using namespace std; int main() { // declare variables int number=0; int counter=1; // get data from user cout<<"Enter a number: "; cin>>number; // this is the start of the nested loop // NOTE: many use two nested 'for' loops, but // sometimes its nice to switch things up while(counter <= number) { for(int x=1; x <= counter; ++x) { cout<<number*x<<" "; } cout<<endl; ++counter; } return 0; }// http://programmingnotes.org/ |
SAMPLE OUTPUT:
Enter a number: 9
9
9 18
9 18 27
9 18 27 36
9 18 27 36 45
9 18 27 36 45 54
9 18 27 36 45 54 63
9 18 27 36 45 54 63 72
9 18 27 36 45 54 63 72 81
======= PRINTING AN UPSIDE-DOWN TRIANGLE =======
This program is similar to the first one, this time printing the triangle upside-down.
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#include <iostream> using namespace std; int main() { // declare variables int number=0; int counter=0; int copy=0; // get data from user cout<<"Enter a number: "; cin>>number; // this variable is just a copy // of the number that the user just entered // which will be used in the nested loop copy=number; // this is the start of the nested loop // NOTE: many use two nested 'for' loops, but // sometimes its nice to switch things up while(counter <= number) { for(int x=1; x <= copy; ++x) { cout<<"* "; } cout<<endl; --copy; ++counter; } return 0; }// http://programmingnotes.org/ |
SAMPLE OUTPUT:
Enter a number: 9
* * * * * * * * *
* * * * * * * *
* * * * * * *
* * * * * *
* * * * *
* * * *
* * *
* *
*
======= PRINTING AN UPSIDE-DOWN TRIANGLE WITH NUMBERS =======
This program is similar to the second one, this time printing the triangle upside-down.
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#include <iostream> using namespace std; int main() { // declare variables int number=0; int counter=1; int copy=0; // get data from user cout<<"Enter a number: "; cin>>number; // this variable is just a copy // of the number that the user just entered // which will be used in the nested loop copy=number; // this is the start of the nested loop // NOTE: many use two nested 'for' loops, but // sometimes its nice to switch things up while(counter <= number) { for(int x=1; x <= copy; ++x) { cout<<copy<<" "; } cout<<endl; --copy; ++counter; } return 0; }// http://programmingnotes.org/ |
SAMPLE OUTPUT:
Enter a number: 9
9 9 9 9 9 9 9 9 9
8 8 8 8 8 8 8 8
7 7 7 7 7 7 7
6 6 6 6 6 6
5 5 5 5 5
4 4 4 4
3 3 3
2 2
1
======= PRINTING AN UPSIDE-DOWN TRIANGLE WITH NUMBERS IN-ORDER =======
The following program uses the same concept as above, but this time instead of using stars “*”, numbers will be printed to the screen in-order.
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#include <iostream> using namespace std; int main() { // declare variables int number=0; int counter=1; int copy=0; // get data from user cout<<"Enter a number: "; cin>>number; copy=number; // this is the start of the nested loop. // NOTE: many use two nested 'for' loops, but // sometimes its nice to switch things up while(counter <= number) { for(int x=counter; x <= copy; ++x) { cout<<x<<" "; } cout<<endl; ++counter; } return 0; }// http://programmingnotes.org/ |
SAMPLE OUTPUT:
Enter a number: 9
1 2 3 4 5 6 7 8 9
2 3 4 5 6 7 8 9
3 4 5 6 7 8 9
4 5 6 7 8 9
5 6 7 8 9
6 7 8 9
7 8 9
8 9
9
===== PRINTING AN UPSIDE-DOWN TRIANGLE WITH NUMBERS USING MULTIPLICATION =====
This program is similar to the third one, this time printing the triangle upside-down.
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#include <iostream> using namespace std; int main() { // declare variables int number=0; int counter=1; int copy=0; // get data from user cout<<"Enter a number: "; cin>>number; // this variable is just a copy // of the number that the user just entered // which will be used in the nested loop copy=number; // this is the start of the nested loop // NOTE: many use two nested 'for' loops, but // sometimes its nice to switch things up while(counter <= number) { for(int x=1; x <= copy; ++x) { cout<<number*x<<" "; } cout<<endl; --copy; ++counter; } return 0; }// http://programmingnotes.org/ |
SAMPLE OUTPUT:
Enter a number: 9
9 18 27 36 45 54 63 72 81
9 18 27 36 45 54 63 72
9 18 27 36 45 54 63
9 18 27 36 45 54
9 18 27 36 45
9 18 27 36
9 18 27
9 18
9
======= PRINTING A SQUARE =======
This program prints a square to the screen.
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#include <iostream> using namespace std; int main() { // declare variables int row=0; int column=0; int number=0; cout<<"Enter the number of rows to be printed: "; cin >> number; row = number; // draw top while (row > 0) { cout<<"*"; --row; } cout<<endl; row = number - 2; column = number; // draw middle while (row > 0) { while (column > 0) { if ((column == number) || (column == 1)) { cout<<"*"; } else { cout<<" "; } --column; } cout<<endl; column = number; --row; } row = number; // draw bottom while (row > 0) { cout<<"*"; --row; } cout<<endl; return 0; }// http://programmingnotes.org/ |
SAMPLE OUTPUT:
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Enter the number of rows to be printed: 9 ********* * * * * * * * * * * * * * * ********* |
======= PRINTING THE LETTER “X” =======
The final program for this page will print a giant letter “X” to the screen.
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#include <iostream> #include <cstdlib> using namespace std; int main() { // declare variables int number=0; int counter1=0; cout<<"Enter the size of the shape: "; cin >> number; // set 'counter1' equal to 'number' counter1=-number; // start of the nested loop while(counter1 <=number) { for (int counter2 = -number; counter2 <= number; ++counter2) { if (abs(counter1) == abs(counter2)) { cout<<"x"; } else { cout<<" "; } } ++counter1; cout<<endl; } return 0; }// http://programmingnotes.org/ |
SAMPLE OUTPUT:
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Enter the size of the shape: 9 x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x |
And there you have it. Simple shapes made possible in C++.
QUICK NOTES:
The highlighted lines are sections of interest to look out for.
The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.
Hi, I'm a software engineer. I write articles about programming and design in my spare time.
the prototype abs is not understandable from me in printing of ‘X’
plse give the sol. to print good morning in style of ‘X’