Challenge: Counting Numbers with 7s

Introduction

Counting numbers is a fundamental skill, but what if we add a twist? Let’s introduce a challenge where we count the occurrences of the digit 7 in a given range of numbers. This article will guide you through the process of solving the “Counting Numbers with 7s” challenge, providing a step-by-step approach to tackle this problem.

Problem Statement

Given a range of numbers from A to B (both inclusive), our goal is to count how many times the digit 7 appears in any number within that range.

Approach

To solve this challenge, we’ll take the following approach:

1. Initialize a counter variable to keep track of the number of occurrences of the digit 7.
2. Iterate through each number in the given range from A to B.
3. For each number, convert it to a string.
4. Check each character in the string representation of the number.
5. If a character equals ‘7’, increment the counter variable.
6. After iterating through all the numbers in the range, the counter will contain the total count of the digit 7.
7. Output the final count.

Pseudocode

Here’s the pseudocode representation of our approach:

function countSevens(A, B):
    counter = 0
    for num in range(A, B + 1):
        numString = str(num)
        for char in numString:
            if char == '7':
                counter += 1
    return counter

Implementation in Python

Now let’s implement the above approach in Python:

<code>def countSevens(A, B):
    counter = 0
    for num in range(A, B + 1):
        numString = str(num)
        for char in numString:
            if char == '7':
                counter += 1
    return counter

# Example usage
A = 1
B = 100
result = countSevens(A, B)
print("Count of sevens between", A, "and", B, "is:", result)

Example Output

For the given example range (A = 1, B = 100), the output will be:

Count of sevens between 1 and 100 is: 20

Conclusion

By following the step-by-step approach outlined in this article, we can solve the “Counting Numbers with 7s” challenge effectively. This challenge helps improve our problem-solving skills and provides an opportunity to practice iteration and string manipulation. Remember to break down the problem into smaller steps, and consider using pseudocode before implementing the solution in your chosen programming language. Happy coding!