++ i和i ++之间的区别 [英] difference between ++i and i++

问题描述

可能的重复项：

什么是更高效的i ++或++ i？

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i ++和++ i在循环中的区别？

您好我正在尝试这两个程序

  void fun（）{
 int k = 0; 
 int i = 10; 
 k =（i ++）+（++ i）; 
 cout<< k<< endl; 
 
} 
输出= 22，因为i ++会给出10和++ i将计算为12 
  

但

  void fun（）{
 int k = 0; 
 int i = 10; 
 k =（++ i）+（++ i）; 
 cout<< k<< endl; 
 
} 
输出= 24 
  

解决方案

注意：您正在调用未定义的行为（在序列点之间修改变量两次）

Possible Duplicates:
What is more efficient i++ or ++i?
How do we explain the result of the expression (++x)+(++x)+(++x)?
Difference between i++ and ++i in a loop?

Hi I am trying these two programs

void fun(){
     int k=0;
     int i=10;
     k = (i++)+(++i);
     cout<<k<<endl;

}
Output = 22 as i++ will give 10 and ++i will evaluate into 12

but

void fun(){
     int k=0;
     int i=10;
     k = (++i)+(++i);
     cout<<k<<endl;

}
Output = 24

It should be 23 I guess or there is sth that I am not able to see

Thanks in advance

解决方案

Note: you are invoking undefined behavior (modifying a variable twice between sequence points)

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