LeetCode-Solutions-in-Cpp17

Solutions to high-frequency interview questions of LeetCode in C++17, taking into account both efficiency and comprehensibility.

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• 用哈希表保存出现过的数，如果再次出现，则继续替换也是重复过程，不能满足快乐数的条件

class Solution {
 public:
  bool isHappy(int n) {
    unordered_set<int> s;
    while (n != 1) {
      n = helper(n);
      if (s.count(n)) {
        return false;
      }
      s.emplace(n);
    }
    return true;
  }

  int helper(int n) {
    int sum = 0;
    while (n) {
      int t = n % 10;
      sum += t * t;
      n /= 10;
    }
    return sum;
  }
};