2634. Filter Elements from Array
Description
Given an integer array arr
and a filtering function fn
, return a filtered array filteredArr
.
The fn
function takes one or two arguments:
arr[i]
- number from thearr
i
- index ofarr[i]
filteredArr
should only contain the elements from the arr
for which the expression fn(arr[i], i)
evaluates to a truthy value. A truthy value is a value where Boolean(value)
returns true
.
Please solve it without the built-in Array.filter
method.
Example 1:
Input: arr = [0,10,20,30], fn = function greaterThan10(n) { return n > 10; } Output: [20,30] Explanation: const newArray = filter(arr, fn); // [20, 30] The function filters out values that are not greater than 10
Example 2:
Input: arr = [1,2,3], fn = function firstIndex(n, i) { return i === 0; } Output: [1] Explanation: fn can also accept the index of each element In this case, the function removes elements not at index 0
Example 3:
Input: arr = [-2,-1,0,1,2], fn = function plusOne(n) { return n + 1 } Output: [-2,0,1,2] Explanation: Falsey values such as 0 should be filtered out
Constraints:
0 <= arr.length <= 1000
-109 <= arr[i] <= 109
Solutions
Solution 1: Traversal
We traverse the array $arr$ and for each element $arr[i]$, if $fn(arr[i], i)$ is true, we add it to the answer array. Finally, we return the answer array.
The time complexity is $O(n)$, where $n$ is the length of the array $arr$. Ignoring the space consumption of the answer, the space complexity is $O(1)$.
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