172. Factorial Trailing Zeroes

class Solution {
public:
    int trailingZeroes(int n)
    {
        int res = 0;
        while (n)
        {
            res += n / 5;
            n /= 5;
        }

        return res;
    }
};

• T: $O(N)$
• S: $O(1)$