LeetCode-in-Java
2629. Function Composition
Easy
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 <= 1000all functions accept and return a single integer
Solution
type F = (x: number) => number
function compose(functions: F[]): F {
return function (x) {
if (functions.length == 0) return x
for (let ind = functions.length - 1; ind >= 0; ind--) {
x = functions[ind](x)
}
return x
}
}
/*
* const fn = compose([x => x + 1, x => 2 * x])
* fn(4) // 9
*/
export { compose }