Module dalpy.arrays

Module that holds classes and functions related to 1 and 2 dimensional arrays.

This module contains the Array and Array2D classes and the sort() function. Array represents a 1D array. Array2D represents a 2D array. sort() can be used to return a sorted copy of an Array.

Examples

Creating an Array, setting its elements, and getting a sorted copy:

a = Array(3)
a[0] = 1
a[1] = 4
a[2] = 2
b = sort(a)

Creating an Array2D and setting its elements:

c = Array2D(3,2)
for i in range(3):
    for j in range(2):
        c[i,j] = i + j

Functions

def sort(a)

Gets a sorted copy of an Array.

This does not sort the Array in place. This runs in O(n * log(n)) time where n is the length of the input Array.

Args

a

An Array to be sorted.

Returns

A sorted (Array) copy of a.

Raises

TypeError

If a is not an Array.

Classes

class Array (length)

Represents a 1D array.

This class represents a 1D fixed length array. It should be used like a Java array. That is, you cannot increase its length, slice it, or index it with negative numbers like a Python list. One cannot iterate over an Array like a Python list either. For example, for e in a will raise a RuntimeError for an Array a. A user should assume that indexing into an Array (either for getting or setting elements) is done in O(1) time with respect to the length of the Array.

Examples

After constructing an Array, one can get an element at a particular index using square brackets [] as follows:

a = Array(2)
b = a[0]

Here, b will store the first element in a.

Similarly, one can set an element of an Array using a combination of [] and the assignment operator =

a = Array(2)
a[0] = 1

Here, the first element of a is set to 1.

Note that an IndexError will be raised in the event one supplies an index in [] that is negative or greater than or equal to the length of the Array.

Initializes an Array to be a particular length.

Each of the length elements of this Array will be set to None. This runs in O(length) time.

Args

length

An integer specifying the length of the Array.

Raises

ValueError

If length < 0.

Methods

def length(self)

Returns the integer length of this Array in O(1) time with respect to the length of the Array.

def sort(self)

Sorts the elements of this Array in place.

Note that this modifies this Array, it does not return a sorted copy. The user must make sure that the elements of the Array can be compared. For example, an empty Array cannot be sorted as NoneType (None) elements cannot be compared. This method runs in O(n * log(n)) time where n is the length of the Array.

class Array2D (num_rows, num_columns)

Represents a 2D Array.

This class represents a 2D array with a fixed number of rows and columns. It should be used like a Java two-dimensional array. That is, you cannot increase its dimensions, slice it, or index it with negative numbers like a Python list. Indexing into an Array2D (either for getting or setting) is done in O(1) time with respect to the dimensions of the Array2D.

Examples

After constructing an Array2D, one can get an element at a particular (row, column) index using square brackets [] as follows:

a = Array2D(2,2)
b = a[0,1]

Here, b will store the element in the second column of the first row of a.

Similarly, one can set an element of an Array2D using a combination of [] and the assignment operator =

a = Array2D(2,2)
a[0,1] = 2

Here, the element in the second column of the first of a is set to 2.

Note that an IndexError will be raised in the event one supplies an index in [] that (i) has a row that is negative or greater than or equal to the number of rows of the Array2D or (ii) a column that is negative or greater than or equal to the number of columns of the Array2D.

Initializes an Array2D to be a particular number of rows and columns.

Each of the num_rows * num_columns elements of this Array will be set to None. This method runs in O(num_rows * num_columns) time.

Args

num_rows

An integer specifying the number of rows this Array2D should have.

num_columns

An integer specifying the number of columns each of the rows of this Array2D should have.

Raises

ValueError

If num_rows <= 0 or num_columns <= 0.

Methods

def columns(self)

Returns integer number of columns in this Array2D in O(1) time w/r/t the dimensions of this Array2D.

def rows(self)

Returns integer number of rows in this Array2D in O(1) time w/r/t the dimensions of this Array2D.