Intermediate Level
Implement the countPrimeNumbersUpToN method that counts all prime numbers from 2 up to the given number.
The input contains an integer n. Your task is to count how many prime numbers are present from 2 up to n, including n if it is prime.
For example, when n = 10, the prime numbers are 2, 3, 5, and 7, so the answer is 4.
Example 1
Input
n (int) =
10Returns (int)
4Example 2
Input
n (int) =
20Returns (int)
8Example 3
Input
n (int) =
1Returns (int)
0Check each number from 2 to n and count it only if it is prime.
To test whether a number is prime, try dividing it by values from 2 up to its square root. If none of those values divide it exactly, it is prime.
Pseudocode:
function countPrimeNumbersUpToN(n):
count = 0
for number from 2 to n:
if isPrime(number):
count++
return count
function isPrime(number):
if number <= 1:
return false
divisor = 2
while divisor * divisor <= number:
if number % divisor == 0:
return false
divisor++
return trueReady to test your solutionRun Code checks your solution against the test cases.Shift + Enter to run