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_762.java
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package com.fishercoder.solutions;
/**
* 762. Prime Number of Set Bits in Binary Representation
*
* Given two integers L and R, find the count of numbers in the range [L, R] (inclusive) having a prime number of set bits in their binary representation.
* (Recall that the number of set bits an integer has is the number of 1s present when written in binary.
* For example, 21 written in binary is 10101 which has 3 set bits. Also, 1 is not a prime.)
Example 1:
Input: L = 6, R = 10
Output: 4
Explanation:
6 -> 110 (2 set bits, 2 is prime)
7 -> 111 (3 set bits, 3 is prime)
9 -> 1001 (2 set bits , 2 is prime)
10->1010 (2 set bits , 2 is prime)
Example 2:
Input: L = 10, R = 15
Output: 5
Explanation:
10 -> 1010 (2 set bits, 2 is prime)
11 -> 1011 (3 set bits, 3 is prime)
12 -> 1100 (2 set bits, 2 is prime)
13 -> 1101 (3 set bits, 3 is prime)
14 -> 1110 (3 set bits, 3 is prime)
15 -> 1111 (4 set bits, 4 is not prime)
Note:
L, R will be integers L <= R in the range [1, 10^6].
R - L will be at most 10000.
*/
public class _762 {
public static class Solution1 {
public int countPrimeSetBits(int L, int R) {
int count = 0;
for (int i = L; i <= R; i++) {
if (hasPrimeNumberSetBits(i)) {
count++;
}
}
return count;
}
private boolean hasPrimeNumberSetBits(int num) {
int k = getSetBits(num);
if (k <= 1) {
return false;
}
for (int i = 2; i * i <= k; i++) {
if (k % i == 0) {
return false;
}
}
return true;
}
private int getSetBits(int n) {
int bits = 0;
while (n != 0) {
bits++;
n &= (n - 1);
}
return bits;
}
}
}