C++ Program to Print Inverted Pyramid Pattern

You can print an inverted pyramid in C++ using nested for loops where the outer loop controls the rows and the inner loops print spaces and stars; for example, use for (int i = n; i >= 1; i--) to print decreasing stars each row.

Examples

Input5

Output***** **** *** ** *

Input3

Output*** ** *

Input1

Output*

How to Think About It

To print an inverted pyramid, start from the full width of stars on the first line and reduce the number of stars by one each line. Add spaces before the stars to keep the shape centered or aligned to the right. Use one loop to count down the rows and nested loops to print spaces and stars accordingly.

Algorithm

1

Get the number of rows (n) from the user

2

For each row from n down to 1:

3

Print spaces equal to (n - current row number)

4

Print stars equal to the current row number

5

Move to the next line

Code

cpp

#include <iostream>
using namespace std;

int main() {
    int n;
    cout << "Enter number of rows: ";
    cin >> n;

    for (int i = n; i >= 1; i--) {
        for (int space = 0; space < n - i; space++)
            cout << ' ';
        for (int star = 0; star < i; star++)
            cout << '*';
        cout << '\n';
    }
    return 0;
}

Output

Enter number of rows: 5
*****
 ****
  ***
   **
    *

Dry Run

Let's trace the program with input 3 through the code

1

Input

User enters n = 3

2

First row (i=3)

Print 0 spaces, then 3 stars: ***

3

Second row (i=2)

Print 1 space, then 2 stars: **

4

Third row (i=1)

Print 2 spaces, then 1 star: *

Row (i)	Spaces (n - i)	Stars (i)	Output line
3	0	3	***
2	1	2	**
1	2	1	*

Why This Works

Step 1: Outer loop controls rows

The outer for loop runs from n down to 1, controlling how many stars to print each line.

Step 2: Print spaces before stars

The first inner loop prints spaces to shift stars right, using n - i spaces to align the pyramid.

Step 3: Print stars

The second inner loop prints stars equal to the current row number i, decreasing each line to form the inverted pyramid.

Alternative Approaches

Using while loops

cpp

#include <iostream>
using namespace std;

int main() {
    int n;
    cout << "Enter number of rows: ";
    cin >> n;

    int i = n;
    while (i >= 1) {
        int space = 0;
        while (space < n - i) {
            cout << ' ';
            space++;
        }
        int star = 0;
        while (star < i) {
            cout << '*';
            star++;
        }
        cout << '\n';
        i--;
    }
    return 0;
}

This uses while loops instead of for loops, which some beginners find easier to understand but can be more verbose.

Right-aligned inverted pyramid without spaces

cpp

#include <iostream>
using namespace std;

int main() {
    int n;
    cout << "Enter number of rows: ";
    cin >> n;

    for (int i = n; i >= 1; i--) {
        for (int star = 0; star < i; star++)
            cout << '*';
        cout << '\n';
    }
    return 0;
}

This prints an inverted pyramid aligned to the left without spaces, simpler but less visually centered.

Complexity: O(n^2) time, O(1) space

Time Complexity

The program uses nested loops where the outer loop runs n times and the inner loops run up to n times, resulting in O(n^2) time.

Space Complexity

Only a few variables are used for counting; no extra space proportional to input size is needed, so space complexity is O(1).

Which Approach is Fastest?

All approaches have similar time complexity; using for loops is concise and clear, while while loops are more verbose but equally efficient.

Approach	Time	Space	Best For
For loops	O(n^2)	O(1)	Clear and concise code
While loops	O(n^2)	O(1)	Beginners learning loop control
No spaces (left-aligned)	O(n^2)	O(1)	Simpler output without alignment