2635. Apply Transform Over Each Element in Array

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題目敘述

Given an integer array arr and a mapping function fn, return a new array with a transformation applied to each element.

The returned array should be created such that returnedArray[i] = fn(arr[i], i).

Please solve it without the built-in Array.map method.

Example 1:

Input: arr = [1,2,3], fn = function plusone(n) { return n + 1; } Output: [2,3,4] Explanation: const newArray = map(arr, plusone); // [2,3,4] The function increases each value in the array by one.

Example 2:

Input: arr = [1,2,3], fn = function plusI(n, i) { return n + i; } Output: [1,3,5] Explanation: The function increases each value by the index it resides in.

Example 3:

Input: arr = [10,20,30], fn = function constant() { return 42; } Output: [42,42,42] Explanation: The function always returns 42.

解題思路

Solution

/**
 * @param {number[]} arr
 * @param {Function} fn
 * @return {number[]}
 */
var map = function(arr, fn) {
    return arr.map((val, index) => val = fn(val, index));
};

function map(arr: number[], fn: (n: number, i: number) => number): number[] {
    return arr.map((val: number, idx: number) => val = fn(val, idx));
};