2634. Filter Elements from Array

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題目敘述

Given an integer array arr and a filtering function fn, return a new array with a fewer or equal number of elements.

The returned array should only contain elements where fn(arr[i], i) evaluated to a truthy value.

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

解題思路

Solution

/**
 * @param {number[]} arr
 * @param {Function} fn
 * @return {number[]}
 */
var filter = function(arr, fn) {
    let ans = [];
    for (let i=0; i<arr.length; i++) {
        if (fn(arr[i], i)){
            ans.push(arr[i]);
        }
    }
    return ans;
};

function filter(arr: number[], fn: (n: number, i: number) => any): number[] {
    const ans: number[] = [];
    for (let i = 0; i < arr.length; i++) {
        if (fn(arr[i], i)){
            ans.push(arr[i]);
        }
    }
    return ans;
};