Nested Loops and Pattern Problems in C Practice Questions with Solutions

Introduction

Nested loops are loops placed inside another loop. They are especially useful for solving pattern problems, working with rows and columns, and processing tables or grids. In this chapter, you will practice nested for loops through 10 progressively designed examples. You will start with simple rectangle patterns and move toward triangles, number patterns, inverted patterns, and practical row-column problems. These examples will help you build the loop logic needed for arrays, matrices, and advanced C programs. Nested Loops and Pattern Problems in C Practice questions with solutions to help you understand the concepts.

Q1. Print a Rectangle of Stars

Problem Statement

Write a C program to print a rectangle containing 4 rows and 5 stars in each row.

Expected pattern:

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

C Program

#include <stdio.h>

int main()
{
    int i, j;

    for (i = 1; i <= 4; i++)
    {
        for (j = 1; j <= 5; j++)
        {
            printf("*");
        }

        printf("\n");
    }

    return 0;
}

Sample Output

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

Explanation

There are two loops.

The outer loop controls rows:

for (i = 1; i <= 4; i++)

The inner loop controls stars in each row:

for (j = 1; j <= 5; j++)

For every row, the inner loop prints 5 stars.

Concepts Covered

Nested for loop
Rows and columns
Pattern printing
Inner loop
Outer loop

Q2. Print a Square of Numbers

Problem Statement

Write a C program to print the following pattern:

C Program

#include <stdio.h>

int main()
{
    int i, j;

    for (i = 1; i <= 4; i++)
    {
        for (j = 1; j <= 4; j++)
        {
            printf("%d", j);
        }

        printf("\n");
    }

    return 0;
}

Sample Output

Explanation

The outer loop creates 4 rows.

The inner loop prints:

1 2 3 4

for every row.

The value of j starts from 1 again whenever a new row begins.

Concepts Covered

Nested loops
Number patterns
Row-column logic
printf()

Q3. Print an Increasing Star Triangle

Problem Statement

Write a C program to print:

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

C Program

#include <stdio.h>

int main()
{
    int i, j;

    for (i = 1; i <= 5; i++)
    {
        for (j = 1; j <= i; j++)
        {
            printf("*");
        }

        printf("\n");
    }

    return 0;
}

Sample Output

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

Explanation

The important part is:

j <= i

When i = 1, the inner loop prints 1 star.

When i = 2, it prints 2 stars.

When i = 3, it prints 3 stars.

So the number of stars increases with every row.

Concepts Covered

Nested loops
Increasing pattern
Row-dependent condition
Pattern logic

Q4. Print an Inverted Star Triangle

Problem Statement

Write a C program to print:

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

C Program

#include <stdio.h>

int main()
{
    int i, j;

    for (i = 5; i >= 1; i--)
    {
        for (j = 1; j <= i; j++)
        {
            printf("*");
        }

        printf("\n");
    }

    return 0;
}

Sample Output

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

Explanation

The outer loop starts from 5 and decreases:

5 → 4 → 3 → 2 → 1

The inner loop prints the number of stars represented by i.

Therefore, every new row contains one fewer star.

Concepts Covered

Nested loops
Reverse loop
Decreasing pattern
i--

Q5. Print a Number Triangle

Problem Statement

Write a C program to print:

C Program

#include <stdio.h>

int main()
{
    int i, j;

    for (i = 1; i <= 5; i++)
    {
        for (j = 1; j <= i; j++)
        {
            printf("%d", j);
        }

        printf("\n");
    }

    return 0;
}

Sample Output

Explanation

The outer loop controls the number of rows.

The inner loop starts at 1 for every row and continues until j <= i.

For example, when:

i = 4

the inner loop prints:

Concepts Covered

Nested loops
Number pattern
Row-dependent loop
Incrementing numbers

Q6. Print the Same Number in Each Row

Problem Statement

Write a C program to print:

C Program

#include <stdio.h>

int main()
{
    int i, j;

    for (i = 1; i <= 5; i++)
    {
        for (j = 1; j <= i; j++)
        {
            printf("%d", i);
        }

        printf("\n");
    }

    return 0;
}

Sample Output

Explanation

This pattern is slightly different from the previous example.

Previously, we printed j:

printf("%d", j);

Here, we print i:

printf("%d", i);

Therefore, every row contains the same number.

For example:

i = 3

The inner loop runs three times and prints:

Concepts Covered

Nested loops
Difference between i and j
Number patterns
Row-based values

Q7. Print a Hollow Rectangle

Problem Statement

Write a C program to print a hollow rectangle of 5 rows and 6 columns.

Expected output:

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

C Program

#include <stdio.h>

int main()
{
    int i, j;

    for (i = 1; i <= 5; i++)
    {
        for (j = 1; j <= 6; j++)
        {
            if (i == 1 || i == 5 || j == 1 || j == 6)
            {
                printf("*");
            }
            else
            {
                printf(" ");
            }
        }

        printf("\n");
    }

    return 0;
}

Sample Output

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

Explanation

A star is printed when the position is on the border.

The condition:

i == 1 || i == 5 || j == 1 || j == 6

means:

First row → print *
Last row → print *
First column → print *
Last column → print *

Otherwise, a space is printed.

Concepts Covered

Nested loops
if-else
Logical OR ||
Rows and columns
Hollow pattern

Q8. Print a Right-Aligned Star Triangle

Problem Statement

Write a C program to print:

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

C Program

#include <stdio.h>

int main()
{
    int i, j;

    for (i = 1; i <= 5; i++)
    {
        for (j = 1; j <= 5 - i; j++)
        {
            printf(" ");
        }

        for (j = 1; j <= i; j++)
        {
            printf("*");
        }

        printf("\n");
    }

    return 0;
}

Sample Output

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

Explanation

This pattern uses two inner loops.

The first inner loop prints spaces:

for (j = 1; j <= 5 - i; j++)

The second inner loop prints stars:

for (j = 1; j <= i; j++)

For the first row:

4 spaces + 1 star

For the second row:

3 spaces + 2 stars

and so on.

Concepts Covered

Nested loops
Multiple inner loops
Spaces
Right alignment
Pattern design

Q9. Print a Number Pyramid

Problem Statement

Write a C program to print the following pattern:

C Program

#include <stdio.h>

int main()
{
    int i, j;

    for (i = 1; i <= 5; i++)
    {
        for (j = 1; j <= 5 - i; j++)
        {
            printf(" ");
        }

        for (j = 1; j <= 2 * i - 1; j++)
        {
            printf("%d", j);
        }

        printf("\n");
    }

    return 0;
}

Sample Output

Explanation

There are two important calculations.

Spaces

The number of spaces is:

5 - i

Numbers

The number of numbers is:

2 × i - 1

For example, when i = 3:

Spaces = 5 - 3 = 2
Numbers = 2 × 3 - 1 = 5

So the row becomes:

Concepts Covered

Nested loops
Multiple inner loops
Mathematical expressions
Spaces
Pyramid pattern

Q10. Print a Multiplication Table Grid

Problem Statement

Write a C program to print multiplication tables from 1 to 5 in a grid.

C Program

#include <stdio.h>

int main()
{
    int i, j;

    for (i = 1; i <= 5; i++)
    {
        for (j = 1; j <= 10; j++)
        {
            printf("%d x %d = %d\n", i, j, i * j);
        }

        printf("\n");
    }

    return 0;
}

Sample Output

1 x 1 = 1
1 x 2 = 2
1 x 3 = 3
...
1 x 10 = 10

2 x 1 = 2
2 x 2 = 4
2 x 3 = 6
...
2 x 10 = 20

3 x 1 = 3
...

Explanation

The outer loop controls which table is being printed:

for (i = 1; i <= 5; i++)

The inner loop controls the multiplier:

for (j = 1; j <= 10; j++)

For example:

i = 3
j = 4

produces:

3 x 4 = 12

This same row-column concept is useful later when working with two-dimensional arrays and matrices.

Concepts Covered

Nested loops
Multiplication
Row-column logic
Practical nested-loop application

Key Takeaways

A nested loop is a loop inside another loop.
The outer loop commonly controls rows.
The inner loop commonly controls columns or repeated work.
Pattern problems are a good way to practice nested-loop logic.
i and j are commonly used as outer and inner loop variables.
Spaces can be printed using an additional inner loop.
if-else can be combined with nested loops to create hollow patterns.
Nested loops are useful beyond patterns, including tables, matrices, arrays, and grids.
Always update the loop variables correctly to avoid infinite loops.
printf("\n") is commonly used to move to the next row.
Understanding rows and columns makes two-dimensional array problems easier later.

FAQs

1. What is a nested loop in C?

A nested loop is a loop placed inside another loop.

Example:

for (i = 1; i <= 5; i++)
{
    for (j = 1; j <= 5; j++)
    {
        printf("*");
    }
}

2. Which loop is the outer loop?

The loop written outside another loop is called the outer loop.

In pattern programs, it commonly controls the number of rows.

3. Which loop is the inner loop?

The loop placed inside the outer loop is the inner loop.

It commonly controls the number of columns, spaces, stars, or numbers printed in each row.

4. Why are nested loops used for pattern programs?

Patterns normally contain multiple rows and columns. The outer loop can control the rows while the inner loop controls what is printed inside each row.

5. Can we use `while` loops for pattern problems?

Yes. Pattern problems can be solved using for, while, or do-while loops.

For beginners, for loops are often convenient because initialization, condition, and update are visible together.

6. How do I create a right-aligned pattern?

Usually, print spaces before printing the required characters.

For example:

for (j = 1; j <= 5 - i; j++)
{
    printf(" ");
}

for (j = 1; j <= i; j++)
{
    printf("*");
}

The first loop creates the indentation and the second loop creates the stars.

7. How many times does an inner loop execute?

It depends on the condition of the inner loop.

For example:

for (i = 1; i <= 5; i++)
{
    for (j = 1; j <= i; j++)
    {
        printf("*");
    }
}

The inner loop executes:

1 + 2 + 3 + 4 + 5 = 15

times in total.

Written by Shubhranshu Shekhar, who has trained 20000+ students in coding.

Rishabh Kumar

Introduction

Q1. Print a Rectangle of Stars

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q2. Print a Square of Numbers

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q3. Print an Increasing Star Triangle

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q4. Print an Inverted Star Triangle

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q5. Print a Number Triangle

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q6. Print the Same Number in Each Row

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q7. Print a Hollow Rectangle

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q8. Print a Right-Aligned Star Triangle

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Q9. Print a Number Pyramid

Problem Statement

C Program

Sample Output

Explanation

Spaces

Numbers

Concepts Covered

Q10. Print a Multiplication Table Grid

Problem Statement

C Program

Sample Output

Explanation

Concepts Covered

Key Takeaways

FAQs

1. What is a nested loop in C?

2. Which loop is the outer loop?

3. Which loop is the inner loop?

4. Why are nested loops used for pattern programs?

5. Can we use while loops for pattern problems?

6. How do I create a right-aligned pattern?

7. How many times does an inner loop execute?

Related Posts

5. Can we use `while` loops for pattern problems?