Intro π
Problem solving is an important skill, for your career and your life in general.
That's why I take interesting katas of all levels, customize them and explain how to solve them.
Understanding the Exerciseβ
First, we need to understand the exercise!
If you don't understand it, you can't solve it!.
My personal method:
- Input: What do I put in?
- Output: What do I want to get out?
Today's exercise
Today, another 7 kyu
kata,
meaning we slightly increase the difficulty.
Source: Codewars
Write a function findOddDigits
, that accepts two parameter: n
a number and k
a number.
Given n
, e.g. 123456789111
, and k
, e.g. 5
, return the first k
odd digits in n
, e.g. 13579
.
In the following cases the function should return 0
:
- there are no odd digits in
n
; -
k
is bigger thann
; -
k
is0
; -
k
is bigger than the number of odd digits inn
.
Input: two numbers.
Output: one number.
Thinking about the Solution π
I think I understand the exercise (= what I put into the function and what I want to get out of it).
Now, I need the specific steps to get from input to output.
I try to do this in small baby steps:
- Find all odd digits
- Find the first
k
digits - Handle all edge cases
- Return the number
Example:
- Input:
123456789111, 5
- Find all odd digits:
13579111
- Find the first
k
(=5
) digits:13579
- Return the number:
13579
- Output:
13579
β
Implementation (Explicit) β
function findOddDigits(n, k) {
// k = 0;
// k is bigger than a number of digits in n;
if (k === 0 || k > n) return 0;
// find all odd digits
const str = String(n);
const split = str.split("");
const odds = split.filter((num) => num % 2);
// there are no odd digits in a number n;
// k is bigger than a number of odd digits in n.
if (!odds.length || k > odds.length) return 0;
// find the first `k` digits
const joined = odds.join("");
const sliced = joined.slice(0, k);
// return the number
return Number(sliced);
}
Result
console.log(findOddDigits(123456789111, 5));
// 13579 β
console.log(findOddDigits(0, 100));
// 0 β
Implementation (Implicit) β
function findOddDigits(n, k) {
// find all odd digits
const odds = String(n)
.split("")
.filter((num) => num % 2);
// handle all edge cases
if (k === 0 || k > n || !odds.length || k > odds.length) return 0;
// find the first `k` digits and return them as a number
return Number(odds.join("").slice(0, k));
}
Result
console.log(findOddDigits(123456789111, 5));
// 13579 β
console.log(findOddDigits(0, 100));
// 0 β
Playground β½
You can play around with the code here
Next Part β‘οΈ
Great work!
We learned how to use String
, Number
, split
, join
, filter
, slice
.
I hope you can use your new learnings to solve problems more easily!
Next time, we'll solve another interesting kata. Stay tuned!
If I should solve a specific kata, shoot me a message here.
If you want to read my latest stuff, get in touch with me!
Further Reading π
Questions β
- How often do you do katas?
- Which implementation do you like more? Why?
- Any alternative solution?
Top comments (2)
let stringN = numbers.toString()
let countODD = []
let result = ""
And now in one single (almost readable) line!