C++ Program To Print Triangle Pattern

Triangle patterns are useful for practicing nested loops and understanding how rows, columns, spaces, and symbols are controlled in C++.

• Each pattern uses nested loops to control the number of spaces and symbols printed in every row.
• The number of spaces or stars changes according to the row number to create the required shape.

Right Triangle

For n rows, the ith row contains i stars. The outer loop controls the rows, while the inner loop prints the required number of stars.

Illustration

Input: 4
Output: 
*
* *
* * *
* * * *

#include <iostream>
using namespace std;

int main(){
    int n = 5;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= i; j++)
            cout << "* ";
        cout << endl;
    }
    return 0;
}

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

Inverted Right Triangle

For n rows, the ith row contains n - i + 1 stars. The number of stars decreases by one after every row.

Illustration

Input: 5
Output:
* * * * *
* * * *
* * *
* *
*

#include <iostream>
using namespace std;

int main(){
    int n = 5;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n - i + 1; j++)
            cout << "* ";
        cout << endl;
    }
    return 0;
}

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

Alternative Implementation

The same pattern can also be generated by starting the outer loop from n and decreasing it to 1.

#include <iostream>
using namespace std;

int main()
{
    int n = 5;

    for (int i = n; i >= 1; i--)
    {
        for (int j = 1; j <= i