Leetcode 441 Arranging Coins

Leetcode 441 Arranging Coins

class Solution {
public:
    int arrangeCoins(int n) {
      int rows = 0;
      int count = 1;
      while(n >= count)
      {
         n -= count;
         count ++;
         rows ++;
      }
      return rows;

    }
};

//magic method?
class Solution {
public:
    int arrangeCoins(int n) {
        return floor((-1 + sqrt(8.0 * n + 1)) / 2);
    }
};