代码挑战：幸福数字 - Kotlin

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

方案：

internal class Solution {
    fun isHappy(n: Int): Boolean {
        var temp = n
        val set: MutableSet<Int> = HashSet()
        while (set.add(temp)) {
            var value = 0
            while (temp > 0) {
                value += Math.pow(temp % 10.toDouble(), 2.0).toInt()
                temp /= 10
            }
            temp = value
        }
        return temp == 1
    }
}

测试案例：

@Test
fun test1() {
    val solution = Solution()
    val result = solution.isHappy(19)
    Assert.assertEquals(result, true)
}

@Test
fun test2() {
    val solution = Solution()
    val result = solution.isHappy(4)
    Assert.assertEquals(result, false)
}

@Test
fun test3() {
    val solution = Solution()
    val result = solution.isHappy(123)
    Assert.assertEquals(result, false)
}