Algorithm Puzzles: Happy Number

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Algorithm Puzzles everyday every week sometimes: Happy Number

Puzzle

Puzzle from leetcode:

Solution

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class Solution {
public:
    bool isHappy(int n) {
        std::unordered_set<int> occurredSet;
        occurredSet.insert(n);
        int sum = 0;
        while(n > 0) {
           int digit = n % 10;
           sum += (digit * digit);
           n /= 10;
           if (n == 0) {
               if (sum == 1) {
                   return true;
               }
               if (occurredSet.count(sum) > 0) {
                   return false;
               }
               occurredSet.insert(sum);
               n = sum;
               sum = 0;
           }
        }

        return false;
    }
};

T.C.: O(N)
S.C.: O(N)