# Collection Class

A container that stores a set of unique `double` values in a dynamically allocated array. The array grows by one when I add a number and shrinks by one when I remove one. Duplicates are rejected on add.

Source files: `collection/collection.hpp`, `collection/collection.cpp`, `collection/userInput.cpp`.

## What it does

- `addNumber(double)` adds a value if it is not already present. It allocates a new array one slot larger, copies the old values, appends the new value, and replaces the old array.
- `removeNumber(double)` deletes a value if present. It allocates a new array, copies every element except the matched one, shifting later elements down, and replaces the old array.
- `check(double)` returns the index of a value or `-1` if it is absent.
- `value()` returns the sum of all elements.
- `output()` prints the elements separated by spaces.
- `size()` returns the element count.

The class manages its own heap memory, so it defines the copy constructor, the assignment operator, and the destructor. The copy constructor and assignment both allocate a fresh array and deep-copy the elements, so two collections never share the same buffer. Assignment guards against self-assignment before freeing its array.

## Class layout

```mermaid
classDiagram
    class Collection {
        -double* col_
        -int size_
        +Collection()
        +Collection(const Collection&)
        +operator=(const Collection&) Collection&
        +~Collection()
        +size() int
        +check(double) int
        +addNumber(double) void
        +removeNumber(double) void
        +output() void
        +value() double
    }
```

`col_` points at the heap array. `size_` tracks how many doubles it holds. A default-constructed collection starts empty with a null pointer.

## Driver

`userInput.cpp` runs a small loop. It reads a command and, for add or remove, a number:

- `a <number>` adds the number. If it is already present, it prints `duplicate!`.
- `r <number>` removes the number. If it is absent, it prints `not present!`.
- anything else quits.

After each successful add or remove it prints the current contents and the running total.

```
enter operation [a/r/q] and number: a 4
your numbers: 4 , total value: 4
enter operation [a/r/q] and number: a 6
your numbers: 4 6 , total value: 10
enter operation [a/r/q] and number: a 4
duplicate!
enter operation [a/r/q] and number: r 4
your numbers: 6 , total value: 6
enter operation [a/r/q] and number: q
```

## Build and run

```bash
g++ -std=c++11 collection/*.cpp -o collection
./collection
```

## Known rough edges

`addNumber` and `removeNumber` free the old buffer with `delete` rather than `delete[]`, which is the wrong form for an array allocated with `new[]`. `removeNumber` also allocates `size_ + 1` slots when it only needs `size_ - 1`. The class works for the lab's inputs, and these are noted on the Roadmap page.