Homework 12: Matching Parens

Assigned: Wednesday, March 8, 2006
Due: 8:00 a.m., Tuesday, March 14, 2006

Summary: In this assignment, you will apply stacks to the problem of matching parentheses. vectors.

Purposes: To get you used to using stacks.

Contents:

• The Assignment
• Hints
• Submitting Your Work

The Assignment

In the lab on stacks, you wrote a program that used a stack to ensure that the parentheses in an expression are matched. Extend that program to print out the matches for a single-line expression. For example,

(oh (boy) (I am having) ((so) much) fun matching (parens))
    +---+
          +-----------+
                         +--+
                        +---------+
                                                 +------+
+--------------------------------------------------------+

Your program should also handle erroneous inputs. For example,

())((opened closed) (opened (opened closed) (opened
++
  ?EXTRA CLOSE
    +-------------+
                            +-------------+
                                            +------MISSING CLOSE
                    +------------------------------MISSING CLOSE
   +-----------------------------------------------MISSING CLOSE

Hints

Keep track of your position within the string. When you encounter an opening paren, push the position. When you encounter a closing paren, pop the position and print the string.

You will benefit from a helper method to print the string. You can use a for loop or build a really long string of spaces (and a really long string of dashes), and use substring to extract the proper number of spaces or dashes.

Submitting Your Work

Email me your program.