1. Growing Arrays in C
Russell Stephens

2. O- Notation Notation Name Example O(1) Constant Array index O(log n)
Logarithmic
Binary search
O(n)
Linear
String comparison
O(n log n)
N log n
Quicksort
O(n2)
Quadratic
Simple sorting
O(n3)
Cubic
Matrix multiplication
O(2n)
Exponential
Set partioning

3. Maintaining Arrays
Cost of allocation can be minimized by resizing the array in chunks
Arrays should be gathered together in structs
typedef struct Nameval Nameval;
struct Nameval {
char *name;
int value; };
Struct Nvtab {
int nval;
int max;
Nameval *nameval;
} nvtab;

4. Growing Arrays
nvp = (Nameval *) realloc(nvtab.nameval, (NVGROW*nvtab.max) * sizeof(Nameval));
Realloc grows the array to the current size, and protects the existing elements

5. Realloc Function
Using the realloc function reallocates the memory addresses of the members in the array
Because of this, pointers cannot be used to access members of the array
Instead of pointers you must used subscripts to access members of the array
Array[index]

6. memmove vs memcpy memmove memcpy memmove is always correct
memmove should always be used over memcpy
memcpy is very fast but not always correct
Memcpy can overwrite memory locations if a source and destination overlap

7. Summary Arrays are a simple way to group data
Arrays can provide O(1) access to data
Arrays with a large value of n can be expensive to use and alternates should be used

8. Source
Kernighan, Brian W. and Rob Pike. The Practice of Programming Lucent Technologies.