用>> << & | ~对代码进行优化（很重要的面试题）很穷只有20分 不用详细解答 给出思路就行,该怎么处理

用>> << & | ~对代码进行优化（很重要的面试题）很穷只有20分 不用详细解答 给出思路就行
int a = b * 4;
 
int a = b * 72;
 
int a = b / 8;
 
int a = b % 1;
 
int a = b % 16;
 
int a = ( b * 3) / 8;
 
int a = ( b + c ) /2;
 
int a = ( b % 8 ) * 4 ;
不用详细解答 给出思路就行
谢谢了

------解决方案--------------------
int a = b * 4; =>int a = b<<2;
int a = b * 72 =b*64+b*8; =>int a = b<<6+b<<3;
int a = b / 8; =>int a = b>>3;
int a =b % 1; =>int a = 0;
int a = b % 16; =>int a = b-(b>>4)<<4;
int a = ( b * 3) / 8; =>int a = (b<<2+b<<1)>>3;
int a = ( b + c ) /2; =>int a = (b+c)>>1;
int a = ( b % 8 ) * 4 ; =>int a = (b-(b>>3)<<3)<<2;

 
 
 
 
 
------解决方案--------------------
int a = b * 4; => a = b<<2;
 
int a = b * 72; => a = (b<<6) + (b<<3);
 
int a = b / 8; => a = b>>3;
 
int a = b % 1; => a = 0;
 
int a = b % 16; => a = b & 15;
 
int a = ( b * 3) / 8; => a = ( ( b<<1 ) + b )>>3;
 
int a = ( b + c ) /2; => a = (b+c)>>1;
 
int a = ( b % 8 ) * 4 ; => a = (b & 7)<<2;