5 Phases of Software Life Cycle

Transcription

1 Quiz One Answer Key

2 5 Phases of Software Life Cycle Lecture: 5/12 Question: #1 Waterfall Model Nyhoff, ADTs, Data Structures and Problem Solving with C++, Second Edition, 2005 Pearson Education, Inc. All rights reserved

3 Real World Implementation Prototype: approximate model of the final product Spiral Models: combine prototyping and the waterfall model Agile Methods: Highly popular today SCRUM methodology Break large problem into small ones and deliver incrementally so that final product evolves as pieces are delivered Lecture: 5/12 Question: #2 Nyhoff, ADTs, Data Structures and Problem Solving with C++, Second Edition, 2005 Pearson Education, Inc. All rights reserved

4 Types of Errors Syntax errors Errors in the grammar of the programming language Easy to find, often won t compile or run Run-time errors Happen during program execution Program will typically crash Problematic for embedded systems Logic errors Errors in algorithm design Difficult to find Lecture: 5/12 Question: #3 4

5 Abstract Data Type (ADT) An abstract data type is: 1. A collection of data items (storage structures) 2. Basic operations that can be performed on these items (algorithms) Called abstract because the represented data and the algorithms that operate on it are independent of the implementation (data abstraction) Thinking about what can be done with the data, not how it is done Lecture: 5/12 Question: #4

6 Properties of Lists Can have a single element List of even prime numbers (2) Can have no elements Names of delicious recipe which use kale There can be lists of lists A list of the above lists Lecture: 5/14 Question: #5 We will look at the list as an abstract data type Homogeneous Finite length Sequential elements 6

7 Implementing Operations Constructor Static array allocated at compile time Empty Check if size == 1 Traverse Use a loop from 0 th element to size 1 Insert Shift elements to right of insertion point Delete Shift elements back Lecture: 5/14 Question: #6 Also adjust size up or down 7

8 Operations: Insertion Lecture: 5/14 Question: #6 Insertion To insert 20 after 17 Need address of item before point of insertion predptr points to the node containing 17 Get a new node pointed to by newptr and store 20 in it Set the next pointer of this new node equal to the next pointer in its predecessor, thus making it point to its successor. Reset the next pointer of its predecessor to point to this new node 8

9 Operations: Insertion Insertion also works at end of list pointer member of new node set to null Insertion at the beginning of the list predptr must be set to first pointer member of newptr set to that value first set to value of newptr Lecture: 5/14 Question: #6 In all cases, no shifting of list elements is required! 9

10 Linked Lists - Disadvantages Overhead of links: used only internally, pure overhead If dynamic, must provide destructor copy constructor Assignment operator Lecture: 5/14 Question: #7 No longer have direct access to each element of the list Many sorting algorithms need direct access Binary search needs direct access Access of n th item now less efficient must go through first element, and then second, and then third, etc. 10

11 Linked List Linked list NODE contains Data part stores an element of the list Next part stores link/pointer to next element (when no next element, null value) Lecture: 5/14 Question: #8 11

12 Doubly-Linked Lists Bidirectional lists Nodes have data part, forward and backward link Facilitates both forward and backward traversal Requires pointers to both first and last nodes Lecture: 5/19 Question: #9 12

13 Dynamic-Allocation for List Class Dynamic array constructor template <class T> List<T>::List(const int& capacity=max_size) { _capacity = capacity; _items = new(nothrow) T[_capacity]; _size = 0; assert(_items!= 0); } Static array constructor template <class T> List<T>::List() { _size = 0; } Lecture: 5/14 Question: #10 13

14 The STL list<t> Class Template A sequential container Optimized for insertion and erasure at arbitrary points in the sequence. Implemented as a circular doubly-linked list with head node. Lecture: 5/19 Question: #10 14

15 The STL list<t> Class Template Node structure Lecture: 5/19 Question: #10 struct list_node { pointer next, prev; T data; } 15

16 Multiple-Ordered Lists Lecture: 5/19 Question: #11 Ordered linked list Nodes arranged so data items are in ascending/descending order Straightforward when based on one data field However, sometimes necessary to maintain links with a different ordering Possible solution Separate ordered linked lists but wastes space Better approach Single list Multiple links 16