c++ - If Else 构造

Question

if (a == 1)
    //do something
else if (a == 2)
    //do something
else if (a == 3)
    //do something
else if (a == 4)
    //do something
else if (a == 5)
    //do something
else if (a == 6)
    //do something
else if (a == 7)
    //do something
else if (a == 8)
    //do something    

现在想象一下，我们知道 a 大部分为 7，并且我们在程序中多次执行此代码块。将 (a == 7 ) 检查移动到顶部是否会提高任何时间的性能？即:

if (a == 7)
     //do something
else if (a == 1)
    //do something
else if (a == 2)
    //do something
else if (a == 3)
    //do something

等等。它能改善什么还是只是一厢情愿？

Answer 1

你可以使用switch case来提高程序的性能

switch (a) 
{
    case 1:
    break;    

    case 2:
    break;    

    case 3:
    break;    

    case 4:
    break;    

    case 5:
    break;    

    case 6:
    break;    

    case 7:
    break;    
}