Priorities

This projects aims at practice finding a solution to the following requirement:

Given a list of items (identified i.e. by a name) having a priority. When asked to prioritize produce a list of those items that have the highest priority. When asked again produce a list of those items with the next highest priority.

The Priority is an integer number and a higher number indicates a higher priority. Priorities do not need to be unique among the items.

Examples

The input is given in the form item name - corresponding priority. The numbers before the expected results signify the output after the nth invocation of our oracle. (nothing) represents the empty list

Input

• Item 1 - 1

Should yield:

1. Item 1

2. (nothing)

3 - infinity) (nothing)

Input

• Item 1 - 3
• Item 2 - 2
• Item 3 - 1

Should yield:

1. Item 1 as the result

2. Item 2

3. Item 3

4 - infinity) (nothing)

Input

• Item 1 - 6
• Item 2 - 6
• Item 3 - 1

Should yield:

1. Item 1 and Item 2 as the result

2. Item 3

3 - infinity) (nothing)

Input

• Item 1 - 4
• Item 2 - 3
• Item 3 - 3
• Item 4 - 1

Should yield:

1. Item 1

2. Item 2 and Item 3

3. Item 4

4 - infinity) (nothing)