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Leetcode[202] Happy Number

16 Nov 2015

###Task1 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

###Python

class Solution(object):
    def isHappy(self, n):
        """
        :type n: int
        :rtype: bool
        """
        used = set()
        while n not in used:
            used.add(n)
            if n == 1:
                return True
            n = self.sumDig(n)
        return False
    
    def sumDig(self, n):
        li = []
        while n > 0:
            li.append(n % 10)
            n /= 10
        ret = 0
        for i in range(len(li)):
            ret += li[i] * li[i]
        return ret

###Java

public class Solution {
    
    public int[] getBits(int n) {
        String s = String.valueOf(n);
        int[] bits = new int[s.length()]; //clever
        int i = 0;
        while (n > 0) {
            bits[i++] = n % 10;
            n /= 10;
        }
        return bits;
    }
    
    public int getSqrSum(int n) {
        int res = 0;
        int[] bits = getBits(n);
        for (int i = 0; i < bits.length; i++) {
            res += Math.pow(bits[i], 2);
        }
        return res;
    }
    
    public boolean isHappy(int n) {
        HashSet<Integer> set = new HashSet<Integer>();
        while (!set.contains(n)) {
            set.add(n);
            n = getSqrSum(n);
            if (n == 1) {
                return true;
            }
        }
        
        return false;
    }
}

###Points

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