[LeetCode] Happy Number

標籤：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

解題思路

判斷中間結果是否出現重複即可

實現代碼[C++]

//Rumtime:10msclass Solution {public:    bool isHappy(int n) {        set<int> nums;        while(true)        {            if (n == 1)            {                return true;            }            if (nums.find(n) == nums.end())            {                nums.insert(n);                int sum = 0;                while(n)                {                    int x = n % 10;                    sum += x * x;                    n /= 10;                }                n = sum;            }            else            {                return false;            }        }    }};

實現代碼[Python]

# Runtime:76msclass Solution:    # @param {integer} n    # @return {boolean}    def isHappy(self, n):        SQUARE = dict([(c, int(c)**2) for c in "0123456789"])        s = set()        while n != 1 and n not in s:            s.add(n)            n = sum(SQUARE[d] for d in str(n))        return n == 1

[LeetCode] Happy Number