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How To Solve Sum67 On CodingBat: A Step-by-Step Guide

6 min read 11-15- 2024
How To Solve Sum67 On CodingBat: A Step-by-Step Guide

Table of Contents :

To solve the sum67 problem on CodingBat, you need a clear understanding of how to work with arrays and conditionally sum their elements based on specific rules. This article will walk you through the entire process step by step, helping you develop a solution that meets the requirements of the task.

Understanding the Problem

The goal of the sum67 function is to sum the numbers in an array while ignoring any numbers that are part of a sequence starting with 6 and ending with 7. In other words, if you encounter a 6, you ignore all numbers until you find the next 7.

Problem Breakdown

  • Input: An array of integers (e.g., [1, 2, 2, 6, 99, 99, 7]).
  • Output: The sum of integers in the array, ignoring numbers between 6 and 7 (e.g., the sum for the above example would be 1 + 2 + 2 = 5).

Steps to Solve the Problem

Let's break down the steps to create the sum67 function.

Step 1: Initialize Variables

Before you start processing the array, you'll want to initialize a variable to keep track of the total sum and a flag to indicate whether you're in a 6 to 7 sequence.

def sum67(nums):
    total = 0
    in_skip = False

Step 2: Iterate Through the Array

You need to loop through each element in the nums array. Use a for loop to go through the array index by index.

    for num in nums:

Step 3: Check for 6 and 7

Within the loop, you will need to check if the current number is a 6. If it is, set your flag in_skip to True to indicate that you should skip subsequent numbers until you find a 7.

        if num == 6:
            in_skip = True
        elif num == 7 and in_skip:
            in_skip = False

Step 4: Sum the Numbers

If the current number is not part of a 6 to 7 sequence (i.e., in_skip is False), add the number to your total.

        elif not in_skip:
            total += num

Step 5: Return the Result

After finishing the loop, return the total sum.

    return total

Full Function Code

Putting all the steps together, your sum67 function will look like this:

def sum67(nums):
    total = 0
    in_skip = False
    
    for num in nums:
        if num == 6:
            in_skip = True
        elif num == 7 and in_skip:
            in_skip = False
        elif not in_skip:
            total += num
    
    return total

Example Walkthrough

Let’s see how our function works with an example:

print(sum67([1, 2, 2, 6, 99, 99, 7])) # Output: 5
print(sum67([1, 1, 6, 7, 2])) # Output: 4
print(sum67([1, 6, 2, 2, 7, 7])) # Output: 1
print(sum67([6, 1, 2, 3, 7, 4, 5])) # Output: 15

Explanation of Examples

  1. Example 1: [1, 2, 2, 6, 99, 99, 7]

    • Sum: 1 + 2 + 2 = 5 (ignores 6, 99, 99, and 7).

  2. Example 2: [1, 1, 6, 7, 2]

    • Sum: 1 + 1 + 2 = 4 (only 6 and 7 are skipped).

  3. Example 3: [1, 6, 2, 2, 7, 7]

    • Sum: 1 (ignores 6, 2, 2, 7).

  4. Example 4: [6, 1, 2, 3, 7, 4, 5]

    • Sum: 1 + 2 + 3 + 4 + 5 = 15 (it includes all numbers since they are after the first 7).

Important Notes

  • Edge Cases: Remember to handle cases where 6 and 7 are absent in the array.
  • Negative Numbers: Negative numbers should also be considered and summed if they are not between 6 and 7.

Final Thoughts

By breaking down the problem into smaller steps, we've successfully implemented a function to solve the sum67 challenge on CodingBat. This structured approach can be applied to other coding challenges, improving your problem-solving skills.

Happy coding! 🎉

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