Package g1101_1200.s1175_prime_arrangements

Class Solution

java.lang.Object
g1101_1200.s1175_prime_arrangements.Solution
public class Solution extends java.lang.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
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    numPrimeArrangements(int n)
     

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • numPrimeArrangements

      public int numPrimeArrangements(int n)