LeetCode之Prime Number of Set Bits in Binary Representation（Kotlin）-优快云博客

本文链接：https://blog.youkuaiyun.com/wanglikun7342/article/details/79188693

本文介绍了一个算法，用于计算给定范围内整数的二进制表示中具有质数数量的1位数的数量。通过遍历指定范围内的每个整数，统计其二进制形式中的1位数，并判断该数量是否为质数。

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问题：
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.)

方法：
从L遍历到R，统计数字的1bit位数，对1bit位数和进行质数判断。如果为质数则计数加1，最后输出计数值。包含两个私有方法：1. 获取1bit位个数，2. 判断数字是否为质数。

具体实现：

class PrimeNumberOfSetBitsInBinaryRepresentation {
    fun countPrimeSetBits(L: Int, R: Int): Int {
        var count = 0
        for (i in L..R) {
            if (isPrimeNum(getBits(i))) {
                count++
            }
        }
        return count
    }

    private fun getBits(num: Int): Int {
        var cacheNum = num
        var bits = 0
        while (cacheNum != 0) {
            if (cacheNum % 2 == 1) {
                bits++
            }
            cacheNum /= 2
        }
        return bits
    }

    private fun isPrimeNum(num: Int): Boolean {
        if (num == 1) {
            return false
        } else {
            for (i in 2 until num) {
                if (num % i == 0) {
                    return false
                }
            }
            return true
        }
    }
}

fun main(args: Array<String>) {
    val primeNumberOfSetBitsInBinaryRepresentation = PrimeNumberOfSetBitsInBinaryRepresentation()
    val result = primeNumberOfSetBitsInBinaryRepresentation.countPrimeSetBits(990, 1048)
    println("result: $result")
}