[Solved] Given an integer n, return the number of prime numbers that are strictly less than n.

Question

Given an integer n, return the number of prime numbers that are strictly less than n.

Example 1:

Input: n = 10
Output: 4
Explanation: There are 4 prime numbers less than 10, they are 2, 3, 5, 7.

Example 2:

Input: n = 0
Output: 0

Example 3:

Input: n = 1
Output: 0

Constraints:

  • 0 <= n <= 5 * 106

Python Solution

class Solution:
    def countPrimes(self, n: int) -> int:
        arr = [0]*n
        c=0
        
        for i in range(2,int(n**0.5)+1):
            for j in range(i*i,n,i):
                arr[j]=1
        
        for k in range(2,len(arr)):
            if arr[k]==0:
                c+=1
        return (c)

Abhishek Sharma
Abhishek Sharma

Started my Data Science journey in my 2nd year of college and since then continuously into it because of the magical powers of ML and continuously doing projects in almost every domain of AI like ML, DL, CV, NLP.

Articles: 520

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