给定正整数N ,任务是检查N是否为弱质数。
In number theory, a weak prime is a prime number that is less than the arithmetic mean of nearest prime numbers i.e next and previous prime numbers.
First few weak prime numbers are 3, 7, 13, 19, 23, 31, 43, 47, 61, …
A weak prime Pn can be represented as-
where n is its index in the ordered set of prime numbers.
例子:
Input: N = 13
Output: Yes
13 is 6th prime number, the arithmetic mean of 5th and 7th prime number i.e. 11 and 17 is 14.
13 is less than 14 so 13 is a weak prime.
Input: N = 11
Output: No
方法:
- 如果N不是素数或它是第一个素数,即2,则打印No。
- 否则,找到最接近N的素数(左边一个,右边一个),并将它们的算术平均值存储在mean中。
- 如果N <表示打印是。
- 其他打印号。
下面是上述方法的实现:
C++14
// C++ program to check
// if a given number is weak prime
#include
using namespace std;
// Utility function to check
// if a number is prime or not
bool isPrime(int n)
{
// Corner cases
if (n <= 1)
return false;
if (n <= 3)
return true;
// This is checked so that we can skip
// middle five numbers in below loop
if (n % 2 == 0 || n % 3 == 0)
return false;
for(int i = 5; i * i <= n; i = i + 6)
if (n % i == 0 || n % (i + 2) == 0)
return false;
return true;
}
// Function that returns true
// if n is a weak prime
bool isWeakPrime(int n)
{
// If n is not a prime number or
// n is the first prime then return false
if (!isPrime(n) || n == 2)
return false;
// Initialize previous_prime to n - 1
// and next_prime to n + 1
int previous_prime = n - 1;
int next_prime = n + 1;
// Find next prime number
while (!isPrime(next_prime))
next_prime++;
// Find previous prime number
while (!isPrime(previous_prime))
previous_prime--;
// Arithmetic mean
int mean = (previous_prime +
next_prime) / 2;
// If n is a weak prime
if (n < mean)
return true;
else
return false;
}
// Driver code
int main()
{
int n = 13;
if (isWeakPrime(n))
cout << "Yes";
else
cout << "No";
return 0;
}
// This code is contributed by himanshu77
Java
// Java program to check
// if a given number is weak prime
import java.util.*;
class GFG{
// Utility function to check
// if a number is prime or not
static boolean isPrime(int n)
{
// Corner cases
if (n <= 1)
return false;
if (n <= 3)
return true;
// This is checked so that we can skip
// middle five numbers in below loop
if (n % 2 == 0 || n % 3 == 0)
return false;
for (int i = 5; i * i <= n; i = i + 6)
if (n % i == 0 || n % (i + 2) == 0)
return false;
return true;
}
// Function that returns true
// if n is a weak prime
static boolean isWeakPrime(int n)
{
// If n is not a prime number or
// n is the first prime then return false
if (!isPrime(n) || n == 2)
return false;
// Initialize previous_prime to n - 1
// and next_prime to n + 1
int previous_prime = n - 1;
int next_prime = n + 1;
// Find next prime number
while (!isPrime(next_prime))
next_prime++;
// Find previous prime number
while (!isPrime(previous_prime))
previous_prime--;
// Arithmetic mean
int mean = (previous_prime +
next_prime) / 2;
// If n is a weak prime
if (n < mean)
return true;
else
return false;
}
// Driver code
public static void main(String args[])
{
int n = 13;
if (isWeakPrime(n))
System.out.print("Yes");
else
System.out.print("No");
}
}
// This code is contributed by Code_Mech
Python3
# Python3 program to check if a given
# number is weak prime
# Utility function to check
# if a number is prime or not
def isPrime(n):
# Corner cases
if (n <= 1):
return False
if (n <= 3):
return True
# This is checked so that we can skip
# middle five numbers in below loop
if (n % 2 == 0 or n % 3 == 0):
return False
i = 5
while (i * i <= n):
if (n % i == 0 or n % (i + 2) == 0):
return False
i = i + 6
return True
# Function that returns true
# if n is a weak prime
def isWeakPrime(n):
# declaring variables as global
global next_prime, previous_prime
# If n is not a prime number or n is
# the first prime then return false
if(not isPrime(n) or n == 2):
return False
# Initialize previous_prime to n - 1
# and next_prime to n + 1
previous_prime = n - 1
next_prime = n + 1
# Find next prime number
while(not isPrime(next_prime)):
next_prime += 1
# Find previous prime number
while (not isPrime(previous_prime)):
previous_prime -= 1
# Arithmetic mean
mean = (previous_prime + next_prime) // 2
# If n is a weak prime
if(n < mean):
return True
else:
return False
# Driver code
if __name__ == '__main__':
n = 13
if(isWeakPrime(n)):
print("Yes")
else:
print("No")
# This code is contributed by Shivam Singh
C#
// C# program to check if a given number is weak prime
using System;
class GFG {
// Utility function to check
// if a number is prime or not
static bool isPrime(int n)
{
// Corner cases
if (n <= 1)
return false;
if (n <= 3)
return true;
// This is checked so that we can skip
// middle five numbers in below loop
if (n % 2 == 0 || n % 3 == 0)
return false;
for (int i = 5; i * i <= n; i = i + 6)
if (n % i == 0 || n % (i + 2) == 0)
return false;
return true;
}
// Function that returns true
// if n is a weak prime
static bool isWeakPrime(int n)
{
// If n is not a prime number or
// n is the first prime then return false
if (!isPrime(n) || n == 2)
return false;
// Initialize previous_prime to n - 1
// and next_prime to n + 1
int previous_prime = n - 1;
int next_prime = n + 1;
// Find next prime number
while (!isPrime(next_prime))
next_prime++;
// Find previous prime number
while (!isPrime(previous_prime))
previous_prime--;
// Arithmetic mean
int mean = (previous_prime
+ next_prime)
/ 2;
// If n is a weak prime
if (n < mean)
return true;
else
return false;
}
// Driver code
public static void Main()
{
int n = 13;
if (isWeakPrime(n))
Console.WriteLine("Yes");
else
Console.WriteLine("No");
}
}
Javascript
输出:
Yes