Please answer the questions during the discussion period.
Here we will use the main idea of Levitin 7.1 to implement a radix sort of strings.
public class StringArray
int n; // length of array
int k; // length of each string
String [] a; // the array of n strings, each must be of length k
public void sortBy (int i)
{// does stable sort on array a by the i'th letter of the strings
public void sort()
{// sorts strings in a lexicographically
sortBy method, asuming that all the characters in
all the strings in the StringArray are ASCII (each character is in
the range from 0 through 127 when viewed as a number).
Your method should run in O(n) time, treating 128 as a constant.
It is all right to make a second array of $n$ strings if you like.
Recall that you can cast a character to an int by the
operator ``(int)''
or just by using the character where an int is called for.
sort method using {\it radix sort} as follows: By
applying the different sortBy operations for the various values of
i in the right order, and using the fact that sortBy is
stable, you can sort the strings completely using O(nk) total time.
Give code for this and argue that your code sorts correctly.
Last modified 5 November 2003