Chapter 2, Problem 23RE

Suppose you are given a string str and two positions i and j, where i comes before j. The following pseudocode describes how to swap two letters in a word.

We are given a string str and two positions i and j. (i comes before j)

Set first to the substring from the start of the string to the last position before i.

Set middle to the substring from positions i + 1 to j - 1.

Set last to the substring from position j + 1 to the end of the string.

Concatenate the following five strings: first, the string containing just the character at position j, middle, the string containing just the character at position i, and last.

Check this pseudocode, using the string "Gateway" and positions 2 and 4. Draw a diagram of the string that is being computed, similar to Figure 5.