Happy Number Leetcode

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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

 

 這道題一開始沒有理解題意。。。以為加到個位元如果不是1就算不是happy number了。。。但其實要一直加，直到出現迴圈為止。。。 所以題意也不能想當然啊。理解了之後就好做了。 

public class Solution {    public boolean isHappy(int n) {        int sum = 0;        Set<Integer> s = new HashSet<>();        while (true) {            int tmp = n % 10;            n = n / 10;            sum = sum + tmp * tmp;            if (n == 0) {                if (sum != 1 && s.contains(sum)) {                    break;                } else if (sum == 1) {                    return true;                } else {                    s.add(sum);                    n = sum;                    sum = 0;                }            }        }        return false;    }}

top solution和我的解法差不多，但我感覺我自己的可讀性好些？這是我的錯覺嗎？

Top solution:

public boolean isHappy(int n) {    Set<Integer> inLoop = new HashSet<Integer>();    int squareSum,remain;    while (inLoop.add(n)) {        squareSum = 0;        while (n > 0) {            remain = n%10;            squareSum += remain*remain;            n /= 10;        }        if (squareSum == 1)            return true;        else            n = squareSum;    }    return false;}

它有個比較好的點是hashset裡面如果已經存在了的數字，add方法會返回false，這個之前不知道，學習了。

Happy Number Leetcode