## BJP4 Exercise 14.12: shift

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

Write a method `shift` that takes a stack of integers and an integer n as parameters and that shifts n values from the bottom of the stack to the top of the stack. For example, if a variable called `s` stores the following sequence of values:

```bottom [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] top
```

If we make the call `shift(s, 6);` the method shifts the six values at the bottom of the stack to the top of the stack and leaves the other values in the same order producing:

```bottom [7, 8, 9, 10, 6, 5, 4, 3, 2, 1] top
```

Notice that the value that was at the bottom of the stack is now at the top, the value that was second from the bottom is now second from the top, the value that was third from the bottom is now third from the top, and so on, and that the four values not involved in the shift are now at the bottom of the stack in their original order. If `s` had stored these values instead:

```bottom [7, 23, -7, 0, 22, -8, 4, 5] top
```

If we make the following call: `shift(s, 3);` then `s` should store these values after the call:

```bottom [0, 22, -8, 4, 5, -7, 23, 7] top
```

You are to use one queue as auxiliary storage to solve this problem. You may assume that the parameter n is >= 0 and not larger than the number of elements in the stack.