Weekly Challenge 188

Challenge, My solution

Task 1: Divisible Pairs

Task

You are given list of integers @list of size $n and divisor $k.

Write a script to find out count of pairs in the given list that satisfies the following rules.

The pair (i, j) is eligible if and only if

1. 0 <= i < j < len(list)
2. list[i] + list[j] is divisible by k.

My solution

This seems relatively straight forward. As list is a reserved word in Python, I used nums for the Python version. For this I start with the value of matches as zero. I take the last number off the input using the pop function, and store that as k.

For the i iterator, I start at zero and finish at the second last number. For the j iterator, I start at i+1 and end at the last position. I increase matches if the numbers at the relevant position is divisible by k. And then print the result.

I know some clever eggs are going to use map, which is probably going to be a little faster. In the case of these challenges, some times I'll make code easier to understand over speed.

Examples

$ ./ch-1.py 4 5 1 6 2
2

$ ./ch-1.py 1 2 3 4 2
2

$ ./ch-1.py 1 3 4 5 3
2

$ ./ch-1.py 5 1 2 3 4
2

$ ./ch-1.py 7 2 4 5 4
1

Task 2: Total Zero

Task

You are given two positive integers $x and $y.

Write a script to find out the number of operations needed to make both ZERO. Each operation is made up either of the followings:

• $x = $x - $y if $x >= $y
• $y = $y - $x if $y >= $x (using the original value of $x)

My solution

The hardest part of this challenge was understanding what was required. In particular 'using the original value of $x'. I took this to mean the value of $x that was provided, but it became clear that it meant $x at this particular iteration.

With that out of the way, the code become straight forward. I have a value called count starting at 0, and a loop that continues until both x and y is 0.

For each iteration, I add one to the count value. If x is greater, I take y of it, likewise if y is grexater I take x off it. If x and y are the same, I set them both to zero, as we know that taking the other value from each would result in this.

Examples

$ ./ch-2.py 5 4
5

$ ./ch-2.py 4 6
3

$ ./ch-2.py 2 5
4

$ ./ch-2.py 3 1
3

$ ./ch-2.py 7 4
5