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Homework 7 (Due 11:59pm Thursday, November 5, 2020)

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Preliminaries

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• (10 pts.) boolean contains(int key)  returns true if key is in the list, false otherwise.
• (10 pts.) int reverse() constructs a list that is the reversal of this.
• (10 pts.) int sum()  computes the sum of the elements in the list.
• (10 pts.) double average() computes the average of the elements in the list; returns 0 if the list is empty.
  Hint: you can cast an int to double by using the prefix casting operator (double).
• (10 pts.) IntList notGreaterThan(int bound) returns a list of elements in this list that are less or equal to bound .
• (10 pts.) IntList remove(int key) returns a list of all elements in this list that are not equal to key .
• (10 pts.) IntList subst(int oldN, int newN)  returns a list of all elements in this list with oldN replaced by newN .
• (30 15 pts.) IntList merge(IntList other) merges this list with the input list other, assuming that this list and other are sorted in ascending order. Note that the lists need not have the same length.
  Hint: add a method mergeHelp(ConsIntList other) that does all of the work if one list is non-empty (a ConsIntList). Only mergeHelp is recursive. Use dynamic dispatch on the list that may be empty. Recall that a.merge(b) is equivalent to b.merge(a).  You can formulate help methods as visitors.
• (15 pts.) IntList mergeSort().  Leveraging the merge "method" you just wrote (as a visitor), write mergeSort() that sorts an IntList.  Recall that you need to write a help function that splits a list approximately in two.