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Happy Number 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
这道题一开始没有理解题意。。。以为加到个位数如果不是1就算不是happy number了。。。但其实要一直加，直到出现循环为止。。。
所以题意也不能想当然啊。理解了之后就好做了。
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，但我感觉我自己的可读性好些？这是我的错觉么？
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; }
它有个比较好的点是hashset里面如果已经存在了的数字，add方法会返回false，这个之前不知道，学习了。
Happy Number Leetcode
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