这个循环是如何工作的？我无法理解

Question

for(int i=1;i<=n;){
    f++;
    if((i++==p) || (i++==p))
        break;
}

示例 1：n=7,p=3,f=0；所以f的值应该是1吧？但它给出 f=2 作为输出

示例 2：n=7,p=4,f=0；它给出的输出为 f=2

示例 3：n=7,p=5,f=0；它给出的输出为 f=3

帮我理解一下。

Answer 1

案例 1 当 n=7,p=3,f=0 。让我们在执行 for 循环时查看不同变量的值。

迭代 1

for(int i=1;i<=n;) //here n = 7
{
   f++; //here f becomes 1 that is now we have f = 1
   if((i++==p) || (i++==p)) // variable i is incremented by 1 and becomes 2 because of the 
   //first i++. But note the old value of i(which is 1) is returned by i++. So although 
   //right now i = 2, its old value(which is 1) is compared with the value of variable 
   //p(which is 3). Since 1 and 3 are not equal the next (i++==p) is evaluated. And so 
   //again variable i is incremented and becomes 3. But here also the old value of 
   //i(which is 2) is used to compare with value of variable p(which is still 3). But since
   //2 is not equal to 3 the control flow doesn't go inside the `if` and so `break` is not 
   //executed.

   break;
}

迭代 2

for(int i=1;i<=n;) //here n = 7
{
   f++; //here f becomes 2 that is now we have f = 2
   if((i++==p) || (i++==p)) // Now i is incremented again because of the first i++ and 
   //becomes 4. But here also the old value of variable i(which is 3) is used to compare 
   //with value of variable p(which is 3) and since 3 = 3 the condition is satisfied 
   //and we go inside the `if` statement and `break` is executed. Note at this point 
   //the value of f is 2 .That is why you get f =2 as output.

   break;
}

类似地，您可以计算案例 2，其中 n=7,p=4,f=0; 。

请注意，您can/should为此目的使用了调试器。

这个循环是如何工作的？我无法理解

How does this loop work? I am unable to understand it

c++

loops

for-loop

increment