Question

in an Introduction to Algorithm 2nd edition, I found insertion sort pseudo code

INSERTION-SORT(A)
1   for j <- 2 to length[A]
2       do key <- A[j]
3          //Insert A[j] into the sorted sequence A[1 □ j - 1].
4          i <- j - 1
5          while i > 0 and A[i] > key
6           do A[i+1] <- A[i]
7              i <- i -1
8          A[i + 1] <- key

but I can’t understand how swap works here.

I think it needs a swap operation like this

INSERTION-SORT(A)
1   for j <- 2 to length[A]
2       do key <- A[j]
3          //Insert A[j] into the sorted sequence A[1 □ j - 1].
4          i <- j - 1
5          while i > 0 and A[i] > key
6           do temp <- A[i+1]
7              A[i+1] <- A[i]
8              A[i] <- temp
9              i <- i -1
10         A[i + 1] <- key

did I get something wrong?
please help

Answer 1

What’s happening in insertion sort is not a swap.

It is moving each item greater than the one you want to insert up by one index working down from the end of the currently sorted section, and then inserting the new record at the correct place after the old value is moved up.