Engineering Problem Solving with C , Etter

1
Engineering Problem Solving with C, Etter

• Chapter 6
• One-Dimensional Arrays

2
One Dimensional Arrays

• Arrays
• Sorting Algorithms
• Searching Algorithms
• Character Strings
• The string Class.

3
Arrays

• Definition and Initialization
• Computation and Output
• Function Arguments

4
Definition

• An array is a data structure for storing a
  contiguous block of data.
• All data elements in an array must be of the
  same type.
• Individual elements of the array are specified
  using the array name and an offset.
• In C the offset of the first element is always
  0.

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Definition and Initialization

• Syntax
• data_type identifiersize initialization
  list
• Note size is an integer constant.
• Example
• double m8
• m0 m1 m2 m3 m4 m5 m6
  m7

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Initializing Arrays

• Initializing array elements (initializationgtdecla
  ration)
• char vowels5 'a', 'e', 'i', 'o', 'u'
• bool ansKey true, true, false, true, false,
  false
• char word "Hello"

vowels
ansKey
true
false
false
true
false
true
word
'H'
'e'
'l'
'l'
'o'
'\0'
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Accessing Array Elements

• Offsets are used to access individual elements of
  an array.
• General format
• array_identifieroffset
• Example
• for (int i0 ilt7 i)
• mi double(i) 0.5
• Integer expressions may be used as offsets.

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Functions and arrays

• An array identifier, without subscripts,
  references the starting address(first element) of
  the array.
• In C, arrays are passed by reference. ie the
  starting address is passed, no size information.
• Arrays in C to not know their size.
• Generally we specify an additional parameter
  representing the number of elements in the array.

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Example

• include ltiostreamgt
• using namespace std
• const int MAXSIZE20
• void ReadArr(double a, int count, istream
  in)
• int FindMin(const double a, int count)
• int main( )
• double darrMAXSIZE
• int cnt0, position0
• ReadArr(darr, cnt, cin)
• position FindMin(darr, cnt)
• cout ltlt "The smallest value in the array is "
• ltlt darrposition ltlt endl

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• // This function inputs values into an array
  until EOF or array
• // limit reached
• void ReadArray(double a, int count, istream
  in)
• double temp
• count 0
• in gtgt temp
• while ( (count lt MAXSIZE) !in.eof() )
• acount temp
• count
• in gtgt temp

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• //This function returns the offset of the
  smallest
• //value in an array
• int FindMin(const double a, int size)
• int offsetOfMin 0
• for (int i1 iltsize i)
• if (ai lt aoffsetOfMin )
• offsetOfMin i
• //end if
• //end for
• return offsetOfMin
• //end FindMin

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Sorting Algorithms

• selection sort

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Sorting Algorithms

• Sorting algorithms arrange the data into either
  ascending or descending order, based on the
  values in the array.
• Sorting algorithms to be discussed
• Selection sort

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Selection Sort Algorithm

• Find minimum value, place it in the first
  position.
• Find next minimum value, place it in the second
  position.
• Continue doing this until you have placed the
  second to the largest value in the second to the
  last position.

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Practice!

• Fill in the following table to show how the array
  is sorted into ascending order using the
  selection sort.
• arr0 arr1 arr2
  arr3 arr4

29 45 18 51 36
18 45 29 51 36



swap min and arr0
18 29 45 51 36
18 29 36 51 45
18 29 36 45 51
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Search Algorithms

• unordered lists
• ordered lists

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Searching Unordered Lists

• Simple Sequential Search
• Examine each element starting with the first one
  until
• a match is found.
• end of the list is reached.
• Sequential search can be implemented as
• a function which returns true if item in the
  list, false if item is not in the list.
• a function which returns the location of the item
  if found, or 1 if not found.

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Searching Ordered Lists

• Modified Sequential Search
• examine every element in the list until
• item is found.
• list element is larger/smaller than the item you
  are searching for (search fails).
• Binary Search
• Examine middle element
• if element equals item, item found, return
  location.
• if element is larger than item ignore bottom of
  list.
• if element is smaller than item ignore top of
  list.
• Repeat until
• item is found.
• top and bottom cross over (search failed).

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Example of Binary Search for 48
70
59
56
43
37
28
22
14
11
5
arrtop
arrbot
arrmid
70
59
56
43
37
mid is 7
arrmid
arrbot
arrtop
mid is 5
arrtop
arrbot
43
mid is 6
arr6
43
arrtop
arrbot
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Character Strings

• C style strings
• functions defined in cstring

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C Style Character Strings

• A C style strings is defined as a sequence of
  characters, terminated by the null character.
• When declaring a character array to store a C
  style string, memory must be allocated for the
  null character ('\0').
• Literal string constants are enclosed within
  double quote marks "a string".

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C Style String Input

• Recall that the input operator (gtgt) skips
  whitespace .
• To input strings with embedded whitespace , the
  getline() function can be used as illustrated
• char phraseSIZE
• cin.getline(phrase, SIZE)
• The getline() function reads up to SIZE-1
  characters from the input stream and will insert
  the null character.
• getline() is a member function of what class?

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C STYLE STRING FUNCTIONS

• The Standard C library contains a set of
  predefined functions that operate on C style
  strings.
• These functions are defined in the header
  file cstring
• Commonly used string functions
• strlen()
• strcpy()
• strcat()
• strcmp()

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Example C Style Strings

• include ltiostreamgt
• include ltcstringgt //strcmp(), strcpy(), strcat()
• uses namespace std
• int main()
• char str130 "John", str230 "Johnson"
• char phrase20 "'s shirt was green",
  sentence30
• if (strcmp(str1,str2) lt 0)
• strcpy (sentence, str1) // puts "John" into
  sentence
• else
• strcpy (sentence,str2) // puts "Johnson
  into sentence
• strcat(sentence, phrase)
• cout ltlt "Sentence is " ltlt sentence ltlt endl
• return 0

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The string class

• functions defined in string

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The string class

• The string class implements the concept of a
  character string.
• A string object can increase and decrease its
  size dynamically.
• Numerous operators and functions are defined in
  the string class.

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Common Functions Defined in string

• size( )
• empty( )
• substr (int start, int len)
• c_str()

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Overloaded Operators Defined in string

• relational operators
• lt gt lt gt
• concatenation
• assignment

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Example string class

• include ltiostreamgt
• include ltstringgt
• uses namespace std
• int main()
• string str1 "John", str2 "Johnson"
• string phrase "'s shirt was green", sentence
• if (str1 lt str2)
• sentence str1 // assign "John" to
  sentence
• else
• sentence str2 // assign "Johnson to
  sentence
• sentence phrase // append phrase to sentence
• cout ltlt "Sentence is " ltlt sentence ltlt endl
• return 0