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Language/Type: Java Collections Stacks and Queues
Author: Stuart Reges (on 2014/02/13)

Write a method called equals that takes as parameters two stacks containing lists of integers and that returns true if the two stacks are equal and that returns false otherwise. Two stacks are considered equal if they store the same number of values and those values appear in the same order. Your method is to examine the two stacks but must return them to their original state before terminating.

For example, if the following stack variables are defined:

        s1           bottom [3, 18, 9, 42] top
        s2           bottom [3, 18, 9, 42] top
        s3           bottom [3, 18, 9, 42, 17] top
        s4           bottom [42, 9, 18, 3] top

then the call equals(s1, s2) would return true and the calls equals(s1, s3), equals(s1, s4), equals(s2, s3), and equals(s3, s4) would return false. Two empty stacks would be considered equal to each other.

You are to use one stack as auxiliary storage to solve this problem. You may not use any other auxiliary data structures to solve this problem, although you can have as many simple variables as you like. You may not use recursion to solve this problem. Your method should be efficient by returning false immediately if the two stacks are not of the same size and by not examining more values from the two stacks once it has found a difference. Use the Stack interface and ArrayStack implementation described in the cheat sheet.

Type your solution here:

This is a method problem. Write a Java method as described. Do not write a complete program or class; just the method(s) above.

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