### Count Primes

**Description:**

Count the number of prime numbers less than a non-negative number, **n**

**Credits:**

Special thanks to @mithmatt for adding this problem and creating all test cases.

class Solution

{

public:

int countPrimes(int n)

{

vector<int> a(n);

for(int i=; i<n; i++)

a[i] = i; for(int i=; i * <= n; i++)

{

if(i == )

{

a[i] = ;

continue;

} for(int j = i + i; j < n; j += i)

{

if(a[j] != )

a[j] = ;

}

} int count = ;

for(int i=; i<n; i++)

{

cout << a[i] << " ";

if(a[i] != )

{

count++;

}

}

cout << endl; return count;

}

};

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