Chapter 18, Problem 7PE

Program Plan Intro

Merge Sort

Program plan:

Filename: “MergeSorter.java”

This code snippet creates a class “MergeSorter”. In the code,

• Define a class “MergeSorter”.
  • Declare an array “a”.
  • Declare an array list “l”.
  • Define the constructor “MergeSorter ()”.
    • Set the array “a” equal to “anArray”.
    • Define “l”.
    • Iterate a “for” loop.
      • Set elements of “a” to “l”.
  • Define the constructor “MergeSorter ()”.
    • Set the array “l” equal to “aList”.
  • Define the method “sort()”.
    • If the size of “l” is less than or equal to 1,
      • Return.
    • Create two array lists “first” and “second”.
    • Iterate a “for” loop,
      • Add elements of “l” to “first”.
    • Iterate a “for” loop,
      • Add elements of “l” to “second”.
    • Create generic array “firstSorter”.
    • Create generic array “secondSorter”.
    • Call the method “sort()” on “firstSorter”.
    • Call the method “sort()” on “secondSorter”.
    • Call the method “merge()”.
    • If “a” is not empty,
      • Iterate a “for” loop,
        • Set elements of “l” to “a”.
  • Define the method “merge()”.
    • Declare integer “iFirst”.
    • Declare the variable “iSecond”.
    • Declare a variable “j”.
    • Iterate a “while” loop for merging.
      • if “iFirst” is less than “iSecond”.
        • Set “iFirst” to “l”.
        • Increment “iFirst” by 1.
        • • Else,
            • Set “iSecond” to “l”.
            • Increment “iSecond” by 1.
          • Increment “j” by 1.
    • Iterate a “for” loop.
      • Set the first half values of “l”.
    • Iterate a “for” loop.
      • Set the second half values of “l”.

Filename: “MergeSortTester.java”

This code snippet creates a class “MergeSortTester”. In the code,

• Define a class “MergeSortTester”.
  • Define the “main” method.
  • Define the string array “words[]”.
  • Define the object of “MergeSorter”.
  • Call “sort()”.
  • Print the values in the array “words[]”.
  • Print the expected value.