Leetcode#204count Primes

public class Solution {

public int countprimes (int n) {

int c=0;

if (n<=1)

return C;

else{

for (int j=2;j<=n;j++)

{

int v=0;

for (int i=2;i<=math.sqrt (n); i++)

{

if (j%i==0)

{

V=1;

Break

}

}

if (v==0)

C + +;

}

return C;

}

}

}

Show after submitting algorithm

Status:time Limit exceeded
	Submitted: 0 minutes ago

Last executed input:

1500000

Modify

1. Calculates the number of mass that is less than N, except 2, in which all the even numbers are not prime, so they only judge all the odd

2. For an odd k, determine whether it is a prime number and only consider whether K is divisible by the value in 2~sqrt (k)

3. Because it is an odd number, it only determines whether it is divisible by the odd number in 2~sqrt (k).

public class Solution {

public int countprimes (int n) {

int c=0;

if (n<=2)

return C;

if (n==3)

return ++c;

else{

C + +;

for (int j=3;j<n;j=j+2)

{

int v=0;

for (int i=3;i<=math.sqrt (j); i=i+2)

{

if (j%i==0)

{

V=1;

Break

}

}

if (v==0)

C + +;

}

return C;

}

}

}

Leetcode#204count Primes