This program is a classic program in Tan Haoqiang’s book:

for (i=0;i

(1)

About N/2:

It cycles from zero until it reaches a certain number, for example, N=15, it is 0--7;

If N=16, then 0--8

Why?

Because odd numbers are symmetrical about the middle: for example, 15, there are 8 in the middle, and those on both sides are: 1--7 and

9--15, there are 7 on both sides, and one in the middle< /p>

So the middle one does not need to be cycled, that is, the middle 8 does not need to be exchanged, the two sides are exchanged

And the even number 16, 1--8 and 9--16 are all 8, they can be exchanged directly Just

{

(2)

t=a[i];

Assign the i-th to t

a[i]=a[N-1-i];

Assign the symmetrical value to the i-th one

a[N-1 -i]=t;

Then t (that is, the i-th assignment just now is symmetrical with i)

The swap is completed

}

(3)

About N-1-i

For example 15: Because the first one is 0 (i=0, so ai=a0), so with 0 The symmetrical one is 14 (because it is 15 numbers, so it is numbered 0----14), that is, a0----a14,

a[1]----a[13], a[2]---a[12],………………

So it is

0-----15-1-0

2-----15-1-2

………………

That is, i and N-1-i are swapped