这个循环在C#中执行多少次？

Question

int x = 1;
while (x++ < 5)
{
    if ((x % 2) == 0)
        x += 2;
}

问题是以下循环将执行多少次？我可以看到第1个x等于1,第2个x等于2,第3个x等于4,我认为它会执行3次,但为什么答案是2次？

Answer 1

正如你所说的那样,while循环的主体确实会执行两次,而不是三次.

这就是原因.

我将展开循环,以便我们可以看到会发生什么.

int x = 1;                 // x is now 1
while (x++ < 5)            // read the current value of x, which is 1
                           // then increase x by 1, giving it the value 2
                           // then compare the value we read (1) with 5
                           // since 1 < 5, we will execute the body of
                           // the while loop
{
    if (x % 2 == 0)        // x is equal to 2, "2 % 2" is equal to 0
                           // so execute the body of the if-statement
        x += 2;            // increase x by 2, giving it the value 4
}
// while (x++ < 5)         // read the current value of x, which is 4
                           // then increase x by 1, giving it the value 5
                           // then compare the value we read (4) with 5
                           // since 4 < 5, we will execute the body of
                           // the while loop
{
    if (x % 2 == 0)        // x is equal to 5, "5 % 2" is NOT equal to 0
                           // so do not execute the body of the if-statement
}
// while (x++ < 5)         // read the current value of x, which is 5
                           // then increase x by 1, giving it the value 6
                           // then compare the value we read (5) with 5
                           // since 5 < 5 is not true, we will NOT
                           // execute the body of the while loop

我们已经完成了

最终价值x是6.

所以答案是,正如你所说,while循环的主体执行两次.