Question

2803. Factorial Generator

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Description

Write a generator function that takes an integer n as an argument and returns a generator object which yields the factorial sequence.

The factorial sequence is defined by the relation n! = n * (n-1) * (n-2) * ... * 2 * 1​​​.

The factorial of 0 is defined as 1.

 

Example 1:

Input: n = 5
Output: [1,2,6,24,120]
Explanation: 
const gen = factorial(5)
gen.next().value // 1
gen.next().value // 2
gen.next().value // 6
gen.next().value // 24
gen.next().value // 120

Example 2:

Input: n = 2
Output: [1,2]
Explanation: 
const gen = factorial(2) 
gen.next().value // 1 
gen.next().value // 2 

Example 3:

Input: n = 0
Output: [1]
Explanation: 
const gen = factorial(0) 
gen.next().value // 1 

 

Constraints:

• 0 <= n <= 18

Solutions

Solution 1

function* factorial(n: number): Generator<number> {
  if (n === 0) {
    yield 1;
  }
  let ans = 1;
  for (let i = 1; i <= n; ++i) {
    ans *= i;
    yield ans;
  }
}

/**
 * const gen = factorial(2);
 * gen.next().value; // 1
 * gen.next().value; // 2
 */