BiruLyu

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {

BiruLyu

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {

BiruLyu

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {

BiruLyu

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {

BiruLyu

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
/**
 * Definition for a binary tree node.

BiruLyu

/*
x ^ 0 = x;
x ^ x = 0;
x ^ x ^ x = x;
*/
public class Solution {
    public int singleNumber(int[] nums) {
        
        int res = 0;
        for(int num : nums){

BiruLyu

public class Solution {
    public int[] singleNumber(int[] nums) {
        // Get the XOR of the two numbers we need to find
        int xortwo = 0;
        for(int num : nums){
            xortwo ^= num;
        }
        
        // Get its last set bit
        int mask = xortwo & ( -xortwo );

BiruLyu

public class Solution {
    public int rangeBitwiseAnd(int m, int n) {
        while( m < n){
            n &= (n-1);
        }
        return n;
    }
}

BiruLyu

class Solution {
    public int singleNumber(int[] nums) {
        int x1 = 0, x2 = 0, mask = 0;
        
        for (int n : nums) {
            
            x2 = x2 ^ (x1 & n);
            x1 = x1 ^ n;
            mask = ~ (x2 & x1);
            x1 = x1 & mask;

BiruLyu

/*
The unsigned right shift operator ">>>" shifts a zero into the leftmost position, while the leftmost position after ">>" depends on sign extension.
*/
public class Solution {
    // you need treat n as an unsigned value
    public int reverseBits(int n) {
        if (n == 0) return 0;
        int res = 0;
        for(int i = 0; i < 32; i++){
            res <<= 1;