single-number-ii

Posted 2021-11-28 cherrychenlee

原文地址：https://www.jianshu.com/p/c8612aef41af

时间限制：1秒 空间限制：32768K

题目描述

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?

我的代码

class Solution {
public:
    int singleNumber(int A[], int n) {
        int ones=0, twos=0,threes=0;
        for(int i=0;i<n;i++){
            int cur=A[i];
            twos|=(ones&cur);//在更新ones之前先更新twos
            ones^=cur;
            threes=ones&twos;//既出现1次也出现2次的即出现了3次
            ones&=(~threes);//去除出现3次的
            twos&=(~threes);//去除出现3次的
        }
        return ones;
    }
};

运行时间：4ms
占用内存：592k