68 lines
1.9 KiB
Plaintext
68 lines
1.9 KiB
Plaintext
# Chapter 1
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## Efficiency
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Concerns:
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1. Number of operations
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2. Processor speeds
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3. Storage space
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## Interfaces
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* Interface / abstract data type
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### Queue interface
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* `add(x)` (aka `queue`): add `x` to the queue
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* `remove()` (aka `dequeue`): remove the next value from queue and return it
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* Normal queue: the first element inserted is removed first
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* Priority queue: elements are inserted with a priority, and the smallest
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element is removed. This function is usually called `deleteMin`.
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* LIFO queue: a stack; add and remove are called `push` and `pop`.
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* Deque: generalisation of these
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* `addFirst(x)`
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* `removeFirst(x)`
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* `addLast(x)`
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* `removeLast(x)`
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* Stack: addFirst, removeFirst
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* Queue: addLast, removeFirst
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### List interface
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The List interface subsumes the Queue interface. A list is just a sequence of
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values, and a Queue becomes a special case of it.
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Interface:
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* size()
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* get(i): get i'th element
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* set(i, x): set the i'th element to x
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* add(i, x): insert x at position i
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* remove(i): remove the i'th element
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### USet (unordered sets)
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USets are a collection of unique items in no particular order; this mimics a
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mathematical set.
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Interface:
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* `size()`: returns the number of elements in the set
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* `add(x)`: add x to the set if it doesn't already exist
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* `remove(x)`: remove x from the set if it doesn't already exist
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* `find(y)`: membership test
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Note that y and x may be distinct objects, and only need to satisfy an
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equality test. For example, a dictionary or hashmap is created using a tuple
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`(key, value)`; `find` compares on `key` and two objects are considered equal
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if their keys match.
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### SSet (sorted set)
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A USet where order matters. Its interface only changes in the `find` function:
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* `find(x)`: find the smallest y s.t. y >= x. thereby returning a useful value
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even if x isn't in the set. AKA successor search.
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Difference between USet and SSet |