使用多个if语句或在后面加上许多其他if语句是否更有效? [英] is it more efficient to use multiple if statements or one with lots of else ifs after it?

问题描述

例如，许多if和许多else if在开始的一个if之后.我在下面添加了一些伪代码.

As an example of lots of ifs and many else if after one if at the start. I have added some pseudo code below.

if (x=1)
  print x;
if (x=2)
  print x;
if (x=3)
  print x;

或

if (x=1)
  print x;
else if (x=2)
  print x;
else if (x=3)
  print x;

推荐答案

您的代码无法编译；如果您确实要检查条件，则需要使用==代替=；除效率外，还根据需求使用了这两种技术.您可以在以下情况下使用第一种情况:

Your code won't compile; if you really want to check for conditions you need to use == instead for =; more than efficiency, these two techniques are used depending on the requirements. You can use the first case for the following scenario:

if (x==1)
 //Do something
 // 'x' may change here
if (x==2) // check for next condition
 // Do another thing
 // 'x' may change
if (x==3) // check for another condition
 // Do something more
 //'x' may change

如果x的值未更改，则可以执行第二组代码.这样，一旦找到真实条件，您就可以跳过对其余条件的评估.考虑x=1，因此它不会检查x==2和x==3，这样我们可以减少执行时间.

You can do the second set of code if the value for x is not changing. So that you can skip evaluating the rest of conditions once a true condition is found. Consider x=1 So it won't check for x==2 and x==3 so that we can reduce the execution time.

x=1;
if (x==1) // Evaluates to true;
  // Do Something
  // Exit the if
else if (x==2) // will not check for this
  //Do another thing
else if (x==3) // will not check for this
  //Do another thing

如果要检查的条目更多，则应使用

If you have more entries to check you should use a switch instead of these two.

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