Class Solution
- java.lang.Object
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- g1101_1200.s1175_prime_arrangements.Solution
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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
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Constructor Summary
Constructors Constructor Description Solution()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description int
numPrimeArrangements(int n)
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