Solution to the 14th Project Euler problem – Longest Collatz Sequence - in both Kotlin and Javascript.

The 14th Project Euler problem - Longest Collatz Sequence - is stated as follows. Which starting number, under one million, produces the longest Collatz conjecture sequence?

```
const memoize = fn => {
let cache = {};
return n => cache[n] = cache[n] ? cache[n] : fn(n);
};
const getColatzLength = memoize(n => n <= 1 ? 1 : 1 + getColatzLength(n % 2 === 0 ? n / 2 : n * 3 + 1));
const [first] = new Array(1000000).fill()
.map((_, index) => index)
.map(n => getColatzLength(n))
.map((len, n) => ({len, n}))
.sort((a, b) => b.len - a.len);
```

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