2648. Generate Fibonacci Sequence

2648. Generate Fibonacci Sequence

Write a generator function that returns a generator object which yields the fibonacci sequence.

The fibonacci sequence is defined by the relation Xn = Xn-1 + Xn-2.

The first few numbers of the series are 0, 1, 1, 2, 3, 5, 8, 13.

Example 1.

Input: callCount = 5
Output: [0,1,1,2,3]
Explanation:
const gen = fibGenerator();
gen.next().value; // 0
gen.next().value; // 1
gen.next().value; // 1
gen.next().value; // 2
gen.next().value; // 3

Example 2

Input: callCount = 0
Output: []
Explanation: gen.next() is never called so nothing is outputted

Approach

1. Starting value will be x
2. If length of the functions array is 0 then return the initialValue x
3. Looping through the array from the end ( which is the last index )
4. Each element of the array is function so update the value

How i Solved the Problem

/**
 * @param {Function[]} functions
 * @return {Function}
 */
var compose = function (functions) {
  return function (x) {
    let value = x;
    // if length of the functions array is 0. then return x
    if (functions.length === 0) return x;

    // function should be called right to left
    // pop the array or looping through the array from the end

    for (let i = functions.length - 1; i >= 0; i--) {
      value = functions[i](value);
    }

    return value;
  };
};

/**
 * const fn = compose([x => x + 1, x => 2 * x])
 * fn(4) // 9
 */