#319
Bulb Switcher
specialist · 855 · lc medium +31 · verified · 55.6% accepted · 2,947 likes · top 49%
Description
There are n bulbs that are initially off. You first turn on all the bulbs, then you turn off every second bulb. On the third round, you toggle every third bulb. For the i-th round, you toggle every i bulb. For the n-th round, you only toggle the last bulb.
Return the number of bulbs that are on after n rounds.
Example 1:
Input: n = 3
Output: 1
Explanation: At first, the three bulbs are [off, off, off].
After the first round, the three bulbs are [on, on, on].
After the second round, the three bulbs are [on, off, on].
After the third round, the three bulbs are [on, off, off].
So you should return 1 because there is only one bulb is on.
Example 2:
Input: n = 0
Output: 0
Example 3:
Input: n = 1
Output: 1
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