Created
February 27, 2017 09:32
-
-
Save eugeneglova/721048d0386c9791b1ce81fdb26130c9 to your computer and use it in GitHub Desktop.
tail call recursion optimization for factorial and fibonacci
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| 'use strict'; | |
| const factorial = n => n < 2 ? 1 : n * factorial(n - 1) | |
| // run with --harmony and "use strict" to optimize tail call recursion | |
| const factorialOptimizedTailRecursion = (n, acc = 1) => n < 2 ? acc : factorialOptimizedTailRecursion(n - 1, acc * n) | |
| const n = 100000000 | |
| // console.log(factorial(n)) // RangeError: Maximum call stack size exceeded | |
| console.log(factorialOptimizedTailRecursion(n)) // Infinity | |
| // 1 1 2 3 5 8 13 21 34 55 | |
| const fibonacci = n => n < 2 ? 1 : fibonacci(n - 1) + fibonacci(n - 2) | |
| const fibonacciOptimizedTailRecursion = (n, acc = 1) => n < 2 ? acc : fibonacciOptimizedTailRecursion(n - 1, fibonacciOptimizedTailRecursion(n - 2, acc + 1)) | |
| const fibonacciOptimizedMemoization = (n, acc = {}) => acc[n] ? acc[n] : acc[n] = n < 2 ? 1 : fibonacciOptimizedMemoization(n - 1, acc) + fibonacciOptimizedMemoization(n - 2, acc) | |
| const arr = [10,11,12,13,14,15,16,17,18,19,45] | |
| console.log(arr.map(n => fibonacciOptimizedMemoization(n))) // works immediately | |
| console.log(arr.map(n => fibonacci(n))) // works too long | |
| console.log(arr.map(n => fibonacciOptimizedTailRecursion(n))) // works even a bit longer |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment