1.2 KiB
1.2 KiB
| title |
|---|
| 10001st prime |
Problem 7: 10001st prime
Method:
- A prime number is a number which is divided by 1 and itself.
- We can find a number is prime if it's not divisible by other prime numbers smaller than itself.
Solution:
function nthPrime(n) {
//Primes array which will store all the prime numbers
const primes = [2];
//Num is the number we want to check
let num = 3, isPrime = true;
//Looping until primes array is equal to n
while (primes.length < n){
//All the primes numbers of a number is always <= it's square root
let max = Math.ceil(Math.sqrt(num));
for (let i = 0; primes[i] <= max; i++){
if (num % primes[i] == 0) {
//Looping till we find the prime
isPrime = false;
break;
}
}
//if Prime found, push it to the array
if (isPrime) primes.push(num);
isPrime = true;
//An optimization technique, since we know of all even numbers only 2 is a prime number, we can skip the rest
num+=2;
}
//Returning the last number
return primes[primes.length-1];
}