Discussion About Prime Visits

#1

This is Discussion thread about Prime Visits

#2

what is the error in my code

import java.util.Arrays;
import java.util.Scanner;

public class prime_visit {
static boolean prime[] = new boolean[1000001];

public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    Arrays.fill(prime,false);
    precompute();
    int n=0,a=0,b=0;
    n=scan.nextInt();
    while(n-->0){
        a=scan.nextInt();
        b=scan.nextInt();
        int count=0;
        for(int i=a;i<=b;i++){
            if(i==1)
                continue;
            if(prime[i]==false){
                count++;
            }
        }
        System.out.println(count);
    }
}

public static void precompute(){
    for(int i=2;i<1000001;i++){
        if(prime[i]==true){
            continue;
        }else{
            int mutitple = i*2;
            while(mutitple<1000001){
                prime[mutitple]=true;
                mutitple+=i;
            }
        }
    }
}

}

#3

Why am i getting TLE in the below code

#include
using namespace std;

bool checkPrime(int n,long long int j=2){
if(n<=2){
return (n==2)?true:false;
}
if(n%j==0){
return false;
}
if((j*j)>n)
return true;
return checkPrime(n,j+1);
}

int main() {
int T;
cin>>T;
long long a,b,ans=0;

while(T-- && T<=1000){
	ans=0;
	cin>>a>>b;
	if(a<=1000000 && b<=1000000){
		for(long i=a;i<=b;i++){
			if(checkPrime(i))
				ans++;	
		}
		cout<<ans<<endl;
	}
}
return 0;

}

#6

#include<bits/stdc++.h>
using namespace std;
bool isprime(int n){
// int count = 0;
if( n <= 1)
return false;
for( int j = 2; j <= n/2; j++){
if (n%j == 0){
return false;
}
}
return true;
}
int countprime (int a, int b){
int c =0;
for (int i = a; i <= b; i++){
if ( isprime(i)){
// cout << i << ’ ';
c++;
}
}
return c;
// cout << c << endl;
}

int main() {
int t, a, b;
cin >> t;
while(t>0 && t<=1000){

	cin >> a >> b;
	cout << countprime(a, b) << endl;

	t--;
}
return 0;

}

Two of the three test cases are passing and I’m getting a TLE for the third test case, anyone help