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:
Input: 19 Output: true Explanation: 12 + 92 = 82 82 + 22 = 68 62 + 82 = 100 12 + 02 + 02 = 1
Approach #1: C++.
class Solution { public: bool isHappy(int n) { unordered_set<int> s; s.insert(n); while (1) { int summ = 0; while (n) { int t = n % 10; summ += t*t; n /= 10; } if (summ == 1) return true; if (s.count(summ)) return false; s.insert(summ); n = summ; } } };
Approach #2: Java.
class Solution { public boolean isHappy(int n) { HashSet<Integer> set = new HashSet<Integer>(); set.add(n); while (n != 1) { int result = 0; while (n != 0) { result += Math.pow(n % 10, 2); n /= 10; } if (set.contains(result)) { return false; } set.add(result); n = result; } return true; } }
Approach #3: Python.
class Solution(object): def isHappy(self, n): """ :type n: int :rtype: bool """ mem = set() while n != 1: n = sum([int(i)**2 for i in str(n)]) if n in mem: return False else: mem.add(n) else: return True
Time Submitted | Status | Runtime | Language |
---|---|---|---|
a few seconds ago | Accepted | 28 ms | python |
2 minutes ago | Accepted | 5 ms | java |
8 minutes ago | Accepted | 0 ms | cpp |