leetcode@ [136/137] Single Number & Single Number II

https://leetcode.com/problems/single-number/

Given an array of integers, every element appears twice except for one. Find that single one.

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

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        if(nums.size() == 1) return nums[0];
        
        vector<int> bitNums(32, 0);
        
        int res = 0;
        for(int i=0;i<bitNums.size();++i) {
            for(int j=0;j<nums.size();++j) {
                bitNums[i] += (nums[j] >> i) & 1;
            }
            res |= (bitNums[i] % 2) << i;
        }
        
        return res;        
    }
};

https://leetcode.com/problems/single-number-ii/

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?

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        if(nums.size() == 1) return nums[0];
        
        vector<int> bitNums(32, 0);
        
        int res = 0;
        for(int i=0;i<32;++i) {
            for(int j=0;j<nums.size();++j) {
                bitNums[i] += (nums[j] >> i) & 1;
                cout << ((nums[j] >> i) & 1) << " ";
            }
            cout<<endl;
        }
        
        for(int i=0;i<bitNums.size();++i) {
            res += (bitNums[i] % 3) << i;
        }
        return res;
    }
};