Leetcode | | 137, single number II

Problem:

Given an array of integers, every element appears three times except for one. Find the single one.

Note:
Your algorithm should has a linear runtime complexity. Could you implement it without using extra memory?

Hide TagsBit ManipulationTest instructions: In an array, only one element appears once, the other elements appear k times, (K is odd 3)

Thinking:

(1) This problem applies to the occurrence of odd times, the solution is: each of the number of all numbers of the occurrence of 1 of the number of statistics, the K after the remainder, for the number of bits to be asked in the number of digits (0 or 1),

Convert 2 binary to 10 binary

(2) This problem I assume int is 32 bits, some machines are not 32 bits.

Code

Class Solution {public:    int singlenumber (vector<int>& nums) {        string s;        int a=0x0001;        int count=0;        for (int i=0;i<32;i++)        {for            (int j=0;j<nums.size (); j + +)            {                if ((nums[j]&a)!=0)                    count+ +;            }            S.push_back (' 0 ' +count%3);            a=a<<1;            count=0;        }        return Reverse_string_to_int (s);    } Protected:    int Reverse_string_to_int (string s)    {        int a=1;        int ret=0;        for (int i=0;i<s.size (); i++)        {            ret+= (s.at (i)-' 0 ') *a;            a*=2;        }        return ret;    }};

Leetcode | | 137, single number II