1. Engineering Problem Solving with C++, Etter
Chapter 6
One-Dimensional Arrays
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

2. One Dimensional Arrays
Sorting Algorithms
Searching Algorithms
Character Strings
The string Class.
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

3. Engineering Problem Solving with C++, Second Edition, J. Ingber
Definition and Initialization
Computation and Output
Function Arguments
Arrays
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

4. Engineering Problem Solving with C++, Second Edition, J. Ingber
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.
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

5. Definition and Initialization
Syntax:
data_type identifier[size] [= initialization list];
Note: size is an integer constant.
Example:
double m[8];
m[0] m[1] m[2] m[3] m[4] m[5] m[6] m[7] ?
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

6. Engineering Problem Solving with C++, Second Edition, J. Ingber
Initializing Arrays
Initializing array elements (initialization=>declaration)
char vowels[5] = {'a', 'e', 'i', 'o', 'u'};
bool ansKey[] ={true, true, false, true, false, false};
char word[] = "Hello";
vowels
'a'
'e'
'i'
'o'
'u'
ansKey
true
true
false
true
false
false
word
'H'
'e'
'l'
'l'
'o'
'\0'
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

7. Accessing Array Elements
Offsets are used to access individual elements of an array.
General format:
array_identifier[offset]
Example
for (int i=0; i<=7; ++i)
m[i] = double(i) + 0.5;
Integer expressions may be used as offsets.
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

8. Engineering Problem Solving with C++, Second Edition, J. Ingber
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.
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

9. Engineering Problem Solving with C++, Second Edition, J. Ingber
Example
#include <iostream>
using namespace std;
const int MAXSIZE=20;
void ReadArr(double a[], int& count, istream& in);
int FindMin(const double a[], int count);
int main( ) {
double darr[MAXSIZE];
int cnt=0, position=0;
ReadArr(darr, cnt, cin);
position = FindMin(darr, cnt);
cout << "The smallest value in the array is "
<< darr[position] << endl; }
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

10. Engineering Problem Solving with C++, Second Edition, J. Ingber
// 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 >> temp;
while ( (count < MAXSIZE) && !in.eof() )
{ a[count] = temp;
++count; }
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

11. Engineering Problem Solving with C++, Second Edition, J. Ingber
//This function returns the offset of the smallest
//value in an array
int FindMin(const double a[], int size) {
int offsetOfMin = 0;
for (int i=1; i<size; ++i) {
if (a[i] < a[offsetOfMin] ) {
offsetOfMin = i;
}//end if
}//end for
return offsetOfMin;
}//end FindMin
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

12. Engineering Problem Solving with C++, Second Edition, J. Ingber
selection sort
Sorting Algorithms
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

13. Engineering Problem Solving with C++, Second Edition, J. Ingber
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
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

14. 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.
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

15. Engineering Problem Solving with C++, Second Edition, J. Ingber
Practice!
Fill in the following table to show how the array is sorted into ascending order using the selection sort.
arr[0] arr[1] arr[2] arr[3] arr[4] 29 45 18 51 36
swap min and arr[0]
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

16. Engineering Problem Solving with C++, Second Edition, J. Ingber
unordered lists
ordered lists
Search Algorithms
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

17. 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.
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

18. 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:
top and bottom cross over (search failed).
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

19. Example of Binary Search for 485 11 14 22 28 37 43 56 59 70
arr[top]
arr[mid]
arr[bot] 37 43 56 59 70
mid is 7
arr[top]
arr[mid]
arr[bot]
mid is 5 43 37
arr[top]
arr[bot]
mid is 6 43
arr[6] 43
arr[bot]
arr[top]
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

20. Engineering Problem Solving with C++, Second Edition, J. Ingber
C style strings
functions defined in cstring
Character Strings
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

21. 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".
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

22. Engineering Problem Solving with C++, Second Edition, J. Ingber
C Style String Input
Recall that the input operator (>>) skips whitespace .
To input strings with embedded whitespace , the getline() function can be used as illustrated:
char phrase[SIZE];
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?
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

23. 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()
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

24. Example: C Style Strings
#include <iostream>
#include <cstring> //strcmp(), strcpy(), strcat()
uses namespace std;
int main(){
char str1[30] = "John", str2[30] = "Johnson";
char phrase[20] = "'s shirt was green", sentence[30];
if (strcmp(str1,str2) < 0)
strcpy (sentence, str1); // puts "John" into sentence
else
strcpy (sentence,str2); // puts "Johnson into sentence
strcat(sentence, phrase);
cout << "Sentence is: " << sentence << endl;
return 0; }
Prints
Sentence is: John's shirt is green
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

25. Engineering Problem Solving with C++, Second Edition, J. Ingber
functions defined in string
The string class
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

26. Engineering Problem Solving with C++, Second Edition, J. Ingber
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.
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

27. Common Functions Defined in string
size( )
empty( )
substr (int start, int len)
c_str()
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

28. Overloaded Operators Defined in string
relational operators
< > == <= >=
concatenation
+ +=
assignment =
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber

29. Engineering Problem Solving with C++, Second Edition, J. Ingber
Example: string class
#include <iostream>
#include <string>
uses namespace std;
int main(){
string str1 = "John", str2 = "Johnson";
string phrase = "'s shirt was green", sentence;
if (str1 < str2)
sentence = str1; // assign "John" to sentence
else
sentence = str2; // assign "Johnson to sentence
sentence += phrase; // append phrase to sentence
cout << "Sentence is: " << sentence << endl;
return 0; }
Prints
Sentence is: John's shirt is green
2/23/2019
Engineering Problem Solving with C++, Second Edition, J. Ingber