C++ Programming: From Problem Analysis to Program Design, Fifth Edition Chapter 10: Applications of Arrays and the class vector.

C++ Programming: From Problem Analysis to Program Design, Fifth Edition

Chapter 10: Applications of Arrays and the class

vector

Objectives

In this chapter, you will:

• Explore how to sort an array using the bubble sort, selection sort, and insertion sort algorithms

• Learn how to implement the binary search algorithm

• Become familiar with the vector type

C++ Programming: From Problem Analysis to Program Design, Fifth Edition 2

List Processing

• List: a collection of values of the same type

• Basic list operations:– Search the list for a given item– Sort the list– Insert an item in the list– Delete an item from the list– Print the list


Searching

• Sequential search algorithm


Searching (cont'd.)

• List with 1000 elements– Search item is the second item

• Sequential search makes two key comparisons

– Search item is the 900th item• Sequential search makes 900 key comparisons

– Search item is not in the list• Sequential search makes 1000 key comparisons


Searching (cont'd.)

• Sequential search– Not very efficient for large lists– On average, number of key comparisons

equal to half the size of the list– Does not assume that the list is sorted


Bubble Sort

• list[0]...list[n - 1] – List of n elements, indexed 0 to n - 1


Bubble Sort (cont'd.)

• Series of n - 1 iterations– Successive elements list[index] and list[index + 1] of list are compared

– If list[index] > list[index + 1]• Elements list[index] and list[index + 1]

are swapped

• Smaller elements move toward the top

• Larger elements move toward the bottom













• List of length n– Exactly n(n - 1) / 2 key comparisons– On average n(n - 1) / 4 item assignments

• n = 1000– 500,000 key comparisons– 250,000 item assignments


Selection Sort• Rearrange the list by selecting an element

in the list and moving it to its proper position

• Finds the location of the smallest element in the unsorted portion of the list – Moves it to the top of the unsorted portion of

the list


Selection Sort (cont'd.)





• In the unsorted portion of the list:– Find the location of the smallest element– Move the smallest element to the beginning of

the unsorted list





• List of length n– Exactly n(n - 1) / 2 key comparisons– 3(n - 1) item assignments

• n = 1000– 500,000 key comparisons– 3000 item assignments


Insertion Sort

• Sorts the list by moving each element to its proper place


Insertion Sort (cont'd.)

• Consider the element list[4]– First element of unsorted list– list[4] < list[3]

• Move list[4] to proper location• At list[2]







• During the sorting phase– Array containing the list is divided into two

sublists: sorted and unsorted





• List of length n– About (n2 + 3n – 4) / 4 key comparisons– About n(n – 1) / 4 item assignments

• n = 1000– 250,000 key comparisons– 250,000 item assignments


Binary Search• Much faster than a sequential search

• List must be sorted

• “Divide and conquer”

• Compare search item with middle element– Less than middle: search only upper half of

list– More than middle: search only lower half of

list


Binary Search (cont'd.)






Performance of Binary Search

• L is a sorted list of size 1024– Every iteration of the while loop cuts the size

of the search list by half– At most, 11 iterations to determine whether x is

in L– Binary search will make 22 comparisons at most

• L has1048576 elements– Binary search makes 42 item comparisons at

most


Performance of Binary Search (cont'd.)

• List of length n– Maximum number comparisons 2log2n + 2


vector type (class)

• Only a fixed number of elements can be stored in an array

• Inserting and removing elements causes shifting

• vector type implements a list– vector container – vector– vector object– object


vector type (class) (cont'd.)








Programming Example: Election Results

• Presidential election for the student council of your local university

• Write a program to analyze the data and report the winner

• Four major divisions labeled as Region 1, Region 2, Region 3, and Region 4– Each division has several department

– Each department manages its own voting process and directly reports the results to the election committee


Programming Example: Election Results (cont'd.)

• Desired output:


• Voting is reported in the following form:

Programming Example: Election Results (cont'd.)

• Assume that six candidates are running– Program can be modified to accommodate

any number of candidates

• Data is provided in two files:– candData.txt consists of the names of

candidates– voteData.txt each line consists of voting

results• One entry per line


Programming Example: Input and Output

• Input: Two files, one containing the candidates’ names and the other containing the voting data

• Output: election results in a tabular form and the winner


Programming Example: Problem Analysis

• Program must organize the voting data by region

• Program must calculate total number of votes received by each candidate as well as the total votes cast in the election

• Names of the candidates must appear in alphabetical order


Programming Example: Problem Analysis (cont'd.)

• Data type of a candidate’s name and number of votes are different– Separate arrays

• Use a two-dimensional array to hold the next four columns of the output

• One-dimensional array to hold the total votes received by each candidate


Programming Example: Problem Analysis (cont'd.)


Programming Example: Algorithm Design

• Read the candidates’ names into the array candidatesName

• Sort the array candidatesName• Initialize the arrays votesByRegion and totalVotes

• Process the voting data• Calculate the total votes received by each

candidate• Output the results


Programming Example: Function getCandidatesName()


Programming Example: Function sortCandidateName()


Programming Example: Function initialize()


Programming Example: Process Voting Data

• Get a candidateName, regionNumber, and numberOfVotesForTheCandidate

• Find the row number in the array candidatesName that corresponds to this candidate– This gives the corresponding row number in the

array votesByRegion for this candidate

• Find the column in the array votesByRegion that corresponds to the regionNumber


Programming Example: Process Voting Data (cont'd.)

• Update the appropriate entry in the array votesByRegion by adding the numberOfVotesForTheCandidate


Programming Example: Function binSearch()


Programming Example: Function processVotes()


Programming Example: Function addRegionsVote()


Programming Example: Function printHeading()


Programming Example: Function printResults()

• Initialize sumVotes, largestVotes, and winLoc to 0

• For each row in each array:

• Output the final lines of output


Programming Example: Main Algorithm

• Declare the variables

• Open the input file candData.txt• If the input file does not exist, exit the

program

• Read the data from the file candData.txt into the array candidatesName

• Sort the array candidatesName• Close the file candData.txt and clear the

input streamC++ Programming: From Problem Analysis to Program Design, Fifth Edition 57

Programming Example: Main Algorithm (cont'd.)

• Open the input file voteData.txt• If the input file does not exist, exit the

program

• Initialize the arrays votesByRegion and totalVotes

• Process the voting data and store the results in the array votesByRegion


Programming Example: Main Algorithm (cont'd.)

• Calculate the number of total votes received by each candidate and store the results in the array totalVotes

• Print the heading

• Print the results


Summary

• List– Set of elements of the same type

• Sorting algorithms– Bubble sort– Selection sort– Insertion sort

• Binary search– Compare performance to sequential search

• vector type


C++ Programming: From Problem Analysis to Program Design, Fifth Edition Chapter 10: Applications of Arrays and the class vector.

Documents

list c programming

problem analysis

program design

list processing list

list sequential search

selection sort

list of n elements

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