Prime Number of Set Bits in Binary Representation
算一下bit为1的个数, 然后看下个数是不是prime.
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class Solution { public int countPrimeSetBits(int L, int R) { int count = 0; for(int i = L; i <= R; i++) { if(isPrime(countBit(i))) count++; } return count; } private int countBit(int n) { int res = 0; for(int i = 0 ; i < 32; i++) { if((n & (1 << i)) != 0) res++; } return res; } public boolean isPrime(int number) { if(number < 2) return false; int sqrt = (int) Math.sqrt(number) + 1; for (int i = 2; i < sqrt; i++) { if (number % i == 0) { return false; } } return true; } } |