Algorithm Steamroller - thelastmile/FreeCodeCamp GitHub Wiki
Algorithm Steamroller
:triangular_flag_on_post: Remember to use Read-Search-Ask
if you get stuck. Try to pair program :busts_in_silhouette: and write your own code :pencil:
:checkered_flag: Problem Explanation:
This problem seems simple but you need to make sure to flatten any array, regardless of the level which is what adds a bit of difficulty to the problem.
Relevant Links
:speech_balloon: Hint: 1
You need to check if an element is an array or not.
try to solve the problem now
:speech_balloon: Hint: 2
If you are dealing with an array, then you need flatten it by getting the value inside of the array. This means if you have 4 then instead of returning [4] you need to return 4. If you get [4] then the same, you want the 4. You can access it with arr[index1][index2] to go a level deeper.
try to solve the problem now
:speech_balloon: Hint: 3
You will definitely need recursion or another way to go beyond two level arrays to make the code flexible and not hard-coded to the answers needed. Have fun!
try to solve the problem now
Spoiler Alert!
Solution ahead!
:beginner: Basic Code Solution:
function steamrollArray(arr) {
var flattenedArray = [];
// Create function that adds an element if it is not an array.
// If it is an array, then loops through it and uses recursion on that array.
var flatten = function(arg) {
if (!Array.isArray(arg)) {
flattenedArray.push(arg);
} else {
for (var a in arg) {
flatten(arg[a]);
}
}
};
// Call the function for each element in the array
arr.forEach(flatten);
return flattenedArray;
}
// test here
steamrollArray([1, [2], [3, [4](/thelastmile/FreeCodeCamp/wiki/4)]]);
:rocket: Run Code
Code Explanation:
- Create a new variable to keep flattened arrays.
- Create a function that will add non array elements to the new variable, and for the ones that are array it loops through them to get the element.
- It does that by using recursion, if the element is an array then call the function again with a layer of array deeper to check if it is an array or not. if it is not then push that non-array element to the variable that gets returned. Otherwise, keep going deeper.
- Invoke the function, the first time you will always pass it an array, so it always fall in to the isArray branch
- Return the flattened array.
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:sunflower: Intermediate Code Solution:
function steamrollArray(arr) {
return arr.reduce(function (flat, toFlatten) {
return flat.concat(Array.isArray(toFlatten) ? steamrollArray(toFlatten) : toFlatten);
}, []);
}
// test here
steamrollArray([1, [2], [3, [4](/thelastmile/FreeCodeCamp/wiki/4)]]);
:rocket: Run Code
Code Explanation:
- Use reduce to concatenate each element into the last element
- If the new element is an Array itself call the function recursively to flatten it before merging it with the rest of result
- Pass an empty array to reduce as initial value to make sure even the first element will be processed
- Credit goes to
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:trophy: Credits:
If you found this page useful, you may say thanks to the contributors by copying and pasting the following line in the main chat:
Thanks @Rafase282 for your help with Algorithm: Steamroller
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See :point_right:
Wiki Challenge Solution Template
for reference.