## BJP4 Exercise 14.10: isConsecutive

Language/Type: Java Collections Stacks and Queues
Author: Marty Stepp (on 2016/09/08)

Write a method `isConsecutive` that takes a stack of integers as a parameter and that returns whether or not the stack contains a sequence of consecutive integers starting from the bottom of the stack (returning `true` if it does, returning `false` if it does not). Consecutive integers are integers that come one after the other, as in 5, 6, 7, 8, 9, etc. So if a stack `s` stores the following values:

```bottom [3, 4, 5, 6, 7, 8, 9, 10] top
```

Then the call of `isConsecutive(s)` should return `true`. If the stack had instead contained this set of values:

```bottom [3, 4, 5, 6, 7, 8, 9, 10, 12] top
```

Then the call should return `false` because the numbers 10 and 12 are not consecutive. Notice that we look at the numbers starting at the bottom of the stack. The following sequence of values would be consecutive except for the fact that it appears in reverse order, so the method would return `false`:

```bottom [3, 2, 1] top
```

Your method must restore the stack so that it stores the same sequence of values after the call as it did before. Any stack with fewer than two values should be considered to be a list of consecutive integers. You may use one queue as auxiliary storage to solve this problem.