C++ Chapter 7

initialization list

can be initialized using this; values are stored in array in order in which they appear in the list { }; initialization list cannot exceed array size

two dimensional array

can define one array for multiple sets of data; like a table in a spreadsheet; use two size declarators in definition: const int Rows = 4, Cols = 3; int exams [Rows] [Cols];

off-by-one errors

An ___-____-____ error happens when you use array subscripts that are off by one; can happen when you start subscripts at 1 rather than 0

printing char contents of an array

can display contests of character array by sending its name to cout: char fName[ ] = "Henry"; cout << fName << endl;

recognize array size

common to pass array size so that function knows how many elements to process: showScores(tests, ARRAY_SIZE); array size must also be reflected in prototype, header: void showScores (int [], int); void showScores(int tests[ ], int size)

array assignment

for (i = 0; i< array_size; i++) newTests[i] = tests [i];

printing contests of an array

for other types of arrays, you must print element-by-element: for (i=0; i < ARRAY_SIZE; i++) cout << tests[i] << endl;

partial array initialization

if array is initialized with fewer values than the size declarator, the remaining elements will be set to 0

partially-filled arrays

if it is unknown how much data an array will be holding: -make the array large enough to hold largest expected number of elements -use a counter variable to keep track of the number of items stored in the array

tests[i++]

increment i, no effect on tests

vector<int> numbers {1, 2, 3, 4};

initialize vector with list of values 1, 2, 3, 4

declaring vectors

must #include<vector>

size declarators

named constants are commonly used as size declarators; eases program maintenance when size of array needs to be changed

showScores(tests);

pass array to a function using showScores example

implicit array sizing

Can determine array size by the size of the initialization list: Must use either array size declarator or initialization list at array definition

STL vector

a data type defined in the Standard Template Library; can hold values of any type; automatically adds space as more is needed - no need to determine size at definition; can use [ ] to access elements

scores.push_back(75);

add element 75 to full array/array that had no size definition to score array

resize(elts, val)

add elements to a vector, optionally initialized them

tests[i]++

adds 1 to tests[i]

global array

all elements initialized to 0 by default

local array

all elements uninitialized by default

modifying arrays in function

array names in functions are like reference variables - changes made to array in a function are reflected in actual array in calling function

vector<int> scores(30,0)

declare a vector and initialize all elements to 0

vector<int> finals(scores)

declare a vector initialized to size and contents of another vector

vector<int> scores;

declare a vector to hold int element

vector<int> scores 30

declare a vector with initial size 30

int tests[test];

declare array example

scores.size();

determine size of scores array

swap(vec2)

exchange the contents of two vectors

scores.clear();

remove all contents of vector scores

scores.pop_back();

remove last element from vector scores

capacity()

returns max number of elements a vector can store without allocating more memory

at(elt)

returns the value of the element at position elt in the vector

reverse()

reverse the order of the elements in a vector

comparing arrays

to _________ two arrays, you must compare element-by-element

[ ]

to define a function that takes an array parameter, use empty ___ for array argument

while (!scores.empty())

to determine if vector scores is empty

size of array

total number of bytes allocated for it ; #elements*#bytes each element

parallel arrays

two or more arrays that contain related data; a subscript is used to relate arrays: elements at same subscript are related; may be of different types

2D array initialization

two-dimensional arrays are initialized row-by-row; can omit inner { }, some initial values in a row - array elements without initial value will be set to 0 or null

summing and averaging array elements

use simple loop to add together array elements: int tnum; double average, sum=0; for(tnum=0; tnum<SIZE; tnum++) sum += tests[tnum]; once summed, can compute average: average = sum/size

array

variable that can store multiple values of the same type; values stored in adjacent memory locations; declared using [] operator