[LeetCode] 202. Happy Number

轉自LeetCode

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.

Example: 19 is a happy number

• 12 + 92 = 82
• 82 + 22 = 68
• 62 + 82 = 100
• 12 + 02 + 02 = 1

<Solution>
這題的想法如下

• 按著題目的要求去計算，如果 n = 1 了，就結束迴圈，回傳答案

• 用一個 set 來記錄出現過的數字，如果又出現一樣的數字，代表無法結束，跳出迴圈

code 如下(參考資料)
c++

	class Solution {
	public:
	bool isHappy(int n) {
	unordered_set<int> numSet;
	while(n != 1) {
	int sum = 0;
	while(n) {
	int digit = n % 10;
	sum += digit * digit;
	n /= 10;
	}
	n = sum;
	if(numSet.count(n)) {
	break;
	}
	else {
	numSet.insert(n);
	}
	}
	return n == 1;
	}
	};

view raw happyNumber.cpp hosted with ❤ by GitHub

kotlin

	class Solution {
	fun isHappy(n: Int): Boolean {
	val set = mutableSetOf<Int>()
	var number = n
	var sum = 0
	var digit = 0
	while(number != 1) {
	sum = 0
	while(number > 0) {
	digit = number % 10
	sum += digit * digit
	number /= 10
	}
	number = sum
	if(set.contains(number)) {
	return false
	}
	set.add(number)
	}
	return true
	}
	}

view raw happy_number.kt hosted with ❤ by GitHub