Steamroller
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
Hints
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!
Solutions
Solution 1 (Click to Show/Hide)
function steamrollArray(arr) {
const flattenedArray = [];
// Loop over array contents
for (let i = 0; i < arr.length; i++) {
if (Array.isArray(arr[i])) {
// Recursively flatten entries that are arrays
// and push into the flattenedArray
flattenedArray.push(...steamrollArray(arr[i]));
} else {
// Copy contents that are not arrays
flattenedArray.push(arr[i]);
}
}
return flattenedArray;
};
// test here
steamrollArray([1, [2], [3, [[4]]]]);
Code Explanation
- Create a new variable to keep flattened arrays.
- Loop over the elements of the array
- If the element is an array then call the function again with to flatten the subarray and push the contents of the flattened subarray into the flattened array.
- If the element is not an array, then push that non-array element to the flattened array.
- Return the flattened array.
Relevant Links
Solution 2 (Click to Show/Hide)
function steamrollArray(arr) {
const flat = [].concat(...arr);
return flat.some(Array.isArray) ? steamrollArray(flat) : flat;
}
steamrollArray([1, [2], [3, [[4]]]]);
Code Explanation
- Use spread operator to concatenate each element of
arrwith an empty array - Use
Array.some()method to find out if the new array contains an array still - If it does, use recursion to call
steamrollArrayagain, passing in the new array to repeat the process on the arrays that were deeply nested - If it does not, return the flattened array
Relevant Links
Solution 3 (Click to Show/Hide)
function steamrollArray(arr) {
return arr
.toString()
.replace(",,", ",") // "1,2,,3" => "1,2,3"
.split(",") // ['1','2','3']
.map(function(v) {
if (v == "[object Object]") {
// bring back empty objects
return {};
} else if (isNaN(v)) {
// if not a number (string)
return v;
} else {
return parseInt(v); // if a number in a string, convert it
}
});
}
Code Explanation
- First we turn the array to a string, which will give us a string of numbers separated by a comma, double comma if there was an empty array and literal object text if there was an object, which we can fix later in our if statement.
- We replace the double comma with one, then split it back into an array.
- map through the array and fix object values and convert string numbers to regular numbers.
Solution 4 (Click to Show/Hide)
function steamrollArray(val,flatArr=[]) {
val.forEach(item => {
if (Array.isArray(item)) steamrollArray(item, flatArr);
else flatArr.push(item);
});
return flatArr;
}
Solution 5 (Click to Show/Hide)
function steamrollArray(arr, flatArr = []) {
const elem = arr.pop();
return elem
? !Array.isArray(elem)
? steamrollArray(arr, [elem, ...flatArr])
: steamrollArray(arr.concat(elem), flatArr)
: flatArr;
}