【LeetCode】Single Number题解

public class Solution {
    public int singleNumber(int[] nums){
        if (nums == null){
            return 0;
        }
        int sum  = 0;
        for (int i = 0; i < nums.length; i++){
            sum ^= nums[i];
        }
        return sum;
    }
}

public class Solution {
    public int singleNumber(int[] nums) {
        if (nums == null){
            return 0;
        }
        int res = 0;
        for (int i = 0; i < 32; i++){
            int sum = 0;
            for (int j = 0; j < nums.length; j++){
                sum += (nums[j] >> i) & 1;
            }
            res += ((sum % 3) << i);
        }
        return res;
    }
}

public class Solution {
    public int[] singleNumber(int[] nums) {
        if (nums == null){
            return null;
        }
        HashSet<Integer> hashSet = new HashSet<>(nums.length);
        for (int num : nums) {
            if (!hashSet.add(num)) {
                hashSet.remove(num);
            }
        }
        int[] re = new int[2];
        int i = 0;
        for (Integer integer : hashSet) {
            re[i++] = integer;
        }
        return re;
    }
}