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.
Hint: 1
You need to check if an element is an array or not.
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.
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!
Spoiler Alert!
Solution ahead!
Code Solution 1:
function steamroller(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;
}
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.
Code Solution 2:
function steamroller(arr) {
return arr.reduce(function (flat, toFlatten) {
return flat.concat(Array.isArray(toFlatten) ? steamroller(toFlatten) : toFlatten);
}, []);
}
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 http://stackoverflow.com/a/15030117/1075499
Credits:
If you found this page useful, you can give thanks by copying and pasting this on the main chat: thanks @Rafase282 @sabahang for your help with Algorithm: Steamroller
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