Update bulb-switcher.py

kamyu104 · kamyu104 · commit 7aee010bbc81 · 2015-12-19T20:20:24.000+09:00
diff --git a/Python/bulb-switcher.py b/Python/bulb-switcher.py
@@ -1,6 +1,27 @@
 # Time:  O(1)
 # Space: O(1)
 
+# 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 
+# (turning on if it's off or turning off if
+# it's on). For the nth round, you only 
+# toggle the last bulb. Find how many bulbs 
+# are on after n rounds.
+#
+# Example:
+#
+# Given n = 3. 
+#
+# At first, the three bulbs are [off, off, off].
+# After first round, the three bulbs are [on, on, on].
+# After second round, the three bulbs are [on, off, on].
+# After third round, the three bulbs are [on, off, off]. 
+#
+# So you should return 1, because there is 
+# only one bulb is on.
+
 class Solution(object):
     def bulbSwitch(self, n):
         """
