/* C++ Program to demonstrate use of left shift  
   operator */
#include<stdio.h> 
int main() 
{ 
    // a = 5(00000101), b = 9(00001001) 
    unsigned char a = 5, b = 9;  
  
    // The result is 00001010  
    printf("a<<1 = %d\n", a<<1); 
    
    // The result is 00010010  
    printf("b<<1 = %d\n", b<<1);   
    return 0; 
}

輸出結(jié)果：

a<<1 = 10
b<<1 = 18

2. 右移 >>

取兩個數(shù)字，向右移動第一個操作數(shù)的位，第二個操作數(shù)決定移動的位置。同樣地，右平移( x > > y )等于x除以 2^y.

代碼示例：

/* C++ Program to demonstrate use of right 
   shift operator */
#include<stdio.h> 
  
using namespace std; 
int main() 
{ 
    // a = 5(00000101), b = 9(00001001) 
    unsigned char a = 5, b = 9;  
  
    // The result is 00000010  
       
    printf("a>>1 = %d\n", a>>1); 
    
    // The result is 00000100 
    printf("b>>1 = %d\n", b>>1);   
    return 0; 
}

輸出結(jié)果：

a>>1 = 2
b>>1 = 4

3. 數(shù)字 1 左移 <<

1 << i = 2ⁱ。它只適用于正數(shù)。

代碼示例：

#include<stdio.h> 
int main() 
{  
   int i = 3;   
   printf("pow(2, %d) = %d\n", i, 1 << i); 
   i = 4;   
   printf("pow(2, %d) = %d\n", i, 1 << i); 
   return 0; 
}

輸出結(jié)果：

pow(2, 3) = 8
pow(2, 4) = 16

注意事項：

C++ 左移右移越界情況

左移越界

一個32位的long,值為1，
左移32位 = 1
左移33位= 2
...
左移64位= 1
左移65位= 3

所以左移越界有點向循環(huán)左移，左移Index位--》相當于左移 Index%32位，當然%多少是根據(jù)變量類型來定的

int main() {
 
	long v[2] = {0,0};
	long u1 = 1;
	long u2 = (u1 <<33);
	v[1] |= (u1<<33);
	LOG(sizeof(long))
	cout << u1 <<"," <<u2<< "," << v[1]<< endl;
	std::cin.get();
}

輸出：

右移越界

右移越界，移出去的位都會變成0

#include<iostream>
#include<vector>
#include<unordered_map>
using namespace std;
#define LOG(x) std::cout<<x<<std::endl;
 
int main() {
 
	long v[2] = {0,0};
	long u1 =3;
	long u2 = (u1 >>1);
	v[1] |= (u1>>1);
	LOG(sizeof(long))
	cout << u1 <<"," <<u2<< "," << v[1]<< endl;
	std::cin.get();
}

輸出：