260. Single Number III

• Difficulty: Medium

• Topics: Bit Manipulation

• Similar Questions:

  • Single Number

  • Single Number II

Problem:

Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once.

Example:

Input:  [1,2,1,3,2,5]
Output: [3,5]

Note:

1. The order of the result is not important. So in the above example, [5, 3] is also correct.
2. Your algorithm should run in linear runtime complexity. Could you implement it using only constant space complexity?

Solutions:

class Solution {
public:
    vector<int> singleNumber(vector<int>& nums) {
        int digest = 0;
        for (auto& num : nums) {
            digest ^= num;
        }

        // String from the least significant bit, the first bit set to 1 
        digest &= (-digest);
        vector<int> ret(2, 0);

        for (auto& num : nums) {
            if (num & digest) {
                ret[0] ^= num;
            } else {
                ret[1] ^= num;
            }
        }
        return ret;
    }
};