# 

## 

### 

a=0^a=a^0

0=a^a

a=a^b^b

### 

a=a^b

b=a^b

a=a^b

###  1

a=n&(n-1)

###  1

diff=(n&(n-1))^n

## 

[single-number](https://leetcode-cn.com/problems/single-number/)

> ****

```go
func singleNumber(nums []int) int {
    // 10 ^10 == 00
    // 0
    result:=0
    for i:=0;i ****

```go
func singleNumber(nums []int) int {
	// 1
	var result int
	for i := 0; i < 64; i++ {
		sum := 0
		for j := 0; j < len(nums); j++ {
			// 1
			sum += (nums[j] >> i) & 1
		}
		// 00^10=10 | 
		result ^= (sum % 3)   `nums` 

```go
func singleNumber(nums []int) []int {
    // a=a^b
    // b=a^b
    // a=a^b
    // a^b,diff1

    diff:=0
    for i:=0;i  **num** 0  i  num  i 1 

```go
func countBits(num int) []int {
    res:=make([]int,num+1)

    for i:=0;i  [m, n] 0