Dynamic 2D Array

1
Dynamic 2D Array

• COMP103 Lab 5

2
Dynamic 2D Array

• Not the same as static 2D array!
• Static 2D array array of same size of arrays
• Dynamic 2D array array of various size of arrays

Static
Dynamic
3
Dynamic 2D Array

• A static 2D array is guaranteed to be in a single
  block, e.g. int e23
• Instead you could
• have int k6
• exy will be the same
• as kx 3 y

k5
e12
k4
e11
k3
e10
k2
e02
k1
e01
k0
e00
4
Dynamic 2D Array

• Each dynamic memory allocation can only allocate
  memory for a single element or an array of
  elements
• How to construct a dynamic 2D int array?
• Create an array of pointer to int array (int)
• Create arrays of int one-by-one

5
Dynamic 2D Array

• Example (array of 2 x 3)
• int c new int2
• c0 new int3
• c1 new int3

c10 to c12
1060-106B
c00 to c02
1050-105B
1060
1044
c1
1050
1040
c0
Heap memory
6
Dynamic 2D Array

• Note memory allocation in dynamic 2D array are
  not continuous
• Example (dynamic 2 x 3 array c and static 2 x 3
  array a)
• Access to c03 in dynamic 2D array may be
  failed
• Access to a03 in static 2D array will
  actually accessing a10

7
Dynamic 2D Array

• Memory deallocation (e.g. int array of 2 x 3)
• Similar to allocation
• Delete all arrays of int
• delete c0
• delete c1
• Delete array of pointer to int array
• delete c
• Note reverse order of memory allocation!

8
Dynamic Multi-dimensional Array

• Same principle as dynamic 2D array
• Order of memory allocation
• , int, int, int
• Order of memory deallocation
• int, int, int,

9
String Comparison

• String library provided strcmp(), strncmp() for
  char string
• If you want to develop you own, make sure you
  understand the string concept completely!!
• String is terminated by null character (\0)
• Comparison should stop after null character
• Dont use gt, lt, etc!