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2629. Function Composition
Description
Given an array of functions [f1, f2, f3, ..., fn], return a new function fn that is the function composition of the array of functions.
The function composition of [f(x), g(x), h(x)] is fn(x) = f(g(h(x))).
The function composition of an empty list of functions is the identity function f(x) = x.
You may assume each function in the array accepts one integer as input and returns one integer as output.
Example 1:
Input: functions = [x => x + 1, x => x * x, x => 2 * x], x = 4 Output: 65 Explanation: Evaluating from right to left ... Starting with x = 4. 2 * (4) = 8 (8) * (8) = 64 (64) + 1 = 65
Example 2:
Input: functions = [x => 10 * x, x => 10 * x, x => 10 * x], x = 1 Output: 1000 Explanation: Evaluating from right to left ... 10 * (1) = 10 10 * (10) = 100 10 * (100) = 1000
Example 3:
Input: functions = [], x = 42 Output: 42 Explanation: The composition of zero functions is the identity function
Constraints:
-1000 <= x <= 10000 <= functions.length <= 1000- all functions accept and return a single integer
Solutions
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type F = (x: number) => number; function compose(functions: F[]): F { return function (x) { return functions.reduceRight((acc, fn) => fn(acc), x); }; } /** * const fn = compose([x => x + 1, x => 2 * x]) * fn(4) // 9 */