What is the difference between a = a * (2^3) and a = a << 3?

 What is the difference between a = a * (2^3) and a = a <<3?

在面试题中，经常会问，如何高效的实现某个数值乘以2的n次方，标准答案一般是向左移位n位。

其实，这个跟编译器有关系的。当编译器看到常数2的n次方后，可能会直接优化成左移位操作。大家可以自己调试跟踪一下汇编代码。