Fibonacci

Directions

Print out the n-th entry in the Fibonacci series.
The Fibonacci series is an ordering of numbers where each number is the sum of the proceeding two.
For example, the sequence [0, 1, 1, 2, 3, 5, 8, 13, 21, 34] forms the first ten entries of the Fibonacci series.
examples:

fib(4) //--> 3

Solutions

JS

My Solution

function fib(n) {
    if (n < 2) {
        return n;
    }

    const resultsInverseQueue = [1, 0];

    for (let i = 2; i <= n; i++) {
        const earliest = resultsInverseQueue.pop();
        resultsInverseQueue.unshift(resultsInverseQueue[0] + earliest);
        // NOTE: could even be a one-liner
        // resultsInverseQueue.unshift(resultsInverseQueue[0] + resultsInverseQueue.pop());
    }

    return resultsInverseQueue[0]
}

SG Solution

function memoize(fn) {
    const cache = {};
    return function(...args) {
        if (cache[args]) {
            return cache[args];
        }

        cache[args] = fn.apply(this, args);
        return cache[args];
    }
}

function slowFib(n) {
    if (n < 2) {
        return n;
    }

    return fib(n - 1) + fib(n  - 2);
}

const fib = memoize(slowFib);

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