LeetCode------------single-number-ii
2016-10-04 14:39
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Given an array of integers, every element appears three times except for one. Find that single one.Note:Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?用map的话与上一道的答案可以完全一样。
但是,但是,但是。发现了一个牛逼哄哄的解法,转过来分享下:Single Number的本质,就是用一个数记录每个bit出现的次数,如果一个bit出现两次就归0,这种运算采用二进制底下的位操作^是很自然的。Single Number II中,如果能定义三进制底下的某种位操作,也可以达到相同的效果,Single Number II中想要记录每个bit出现的次数,一个数搞不定就加两个数,用ones来记录只出现过一次的bits,用twos来记录只出现过两次的bits,ones&twos实际上就记录了出现过三次的bits,这时候我们来模拟进行出现3次就抵消为0的操作,抹去ones和twos中都为1的bits。
真的是6得很啊
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