1. Compound Data
CSCE 121
J. Michael Moore

2. Large Sets of Data
What to do?

3. Datatypes
Simple
Compound
int, double, bool, etc.
Homogeneous
Heterogeneous
Array
Vector ?

4. Group of homogeneous elements accessed by an index.
Array/Vector
Group of homogeneous elements accessed by an index.
Vector access with ary.at(index)
Bounds checking
Array and Vector access with ary[index]
No bounds checking

5. Array Really a pointer Variable name is a pointer to the first element
For ary[2]
Conceptually: address of ary + 2*sizeof(array datatype)
Actually: ary + 2 (math is done automatically)
Pointer arithmetic
Must know size of array at compile time
Allows access to elements outside of array bounds
Security problem

6. Vector Preferred over arrays Bounds checking
We’ll use vectors instead of arrays for now.
Bounds checking
Prevents access outside array bounds
Resizable
#include <vector>

7. Vector Must say what type it is e.g. vector<int>
Define size at beginning
vector<int> vec = vector<int>(SIZE);
vector<int> vec = vector<int>(SIZE,INIT_VAL);
Let vector grow as needed
vector<int> vec;
vec.push_back(7);
Increases size by one

8. Vector vector<int> vec; vec.push_back(7);
vec.erase(vec.begin()+index);
vec.at(index); // range checking & harder to read
vec[index]; // no range checking & easier to read

9. Parallel Vectors Book calls them multiple vectors.
Conceptually a set of items with multiple types of information
People
Name
Age
Weight
Separate vectors for name, age and weight.
Each index maps to the same person.
Better way is to use a heterogeneous datatype (e.g. classes)

10. Multi-dimensional Vectors
Matrix calculations
Multi-dimensional data
A vector of vectors
vector< vector<int> > ary2d;
Access
ary2d.at(i).at(j) // safer
ary2d[i][j]
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