g1101_1200.s1175_prime_arrangements

Class Solution

java.lang.Object

g1101_1200.s1175_prime_arrangements.Solution

public class Solution
extends Object

1175 - Prime Arrangements.

Easy

Return the number of permutations of 1 to n so that prime numbers are at prime indices (1-indexed.)

(Recall that an integer is prime if and only if it is greater than 1, and cannot be written as a product of two positive integers both smaller than it.)

Since the answer may be large, return the answer **modulo 10^9 + 7 **.

Example 1:

Input: n = 5

Output: 12

Explanation: For example [1,2,5,4,3] is a valid permutation, but [5,2,3,4,1] is not because the prime number 5 is at index 1.

Example 2:

Input: n = 100

Output: 682289015

Constraints:

• 1 <= n <= 100

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
int	numPrimeArrangements(int n)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

numPrimeArrangements

public int numPrimeArrangements(int n)