Solution O(n)


  • 0
    G

    According to this website, in the end, only the numbers that are perfect squares remain On, since other divisors come in pairs, so if one turns a light on, the other will turn it off.

    class Solution(object):
        def bulbSwitch(self, n):
            """
            :type n: int
            :rtype: int
            """
            res=0
            for i in xrange(1, n+1):
                if i ** 2 <= n:
                    res +=1 
                else:
                    break
    
            return res
    

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