Leetcode 题目解析之 Single Number II

2022-01-14 11:28:27 浏览数 (2)

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?

对于数组{1,1,1,2}来说,分析每一位:

代码语言:javascript复制
0 0 0 1 
0 0 0 1 
0 0 0 1 
0 0 1 0 
…………… 
0 0 1 3 (位数)

可以分析,分别计算每一位1的出现次数n,如果n%3==1,那么结果中这一位就应该是1。

代码语言:javascript复制
    public int singleNumber(int[] nums) {
        int rt = 0, bit = 1;
        for (int i = 0; i < 32; i  ) {
            int count = 0;
            for (int v : nums) {
                if ((v & bit) != 0) {
                    count  ;
                }
            }
            bit <<= 1;
            rt |= (count % 3) << i;
        }
        return rt;
    }

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