One-dimensional and Two-dimensional arrays

One-dimensional and Two-dimensional arrays

What are they and how do they work?

A 1D array, also known as a one-dimensional array, is a list of elements that are arranged in a single row. It's like a line of boxes, where each box holds a value. You can access individual elements in a 1D array by referring to their index position.

​​One-dimensional array

2D array, or a two-dimensional array, is like a grid or a table with rows and columns. It consists of multiple rows and columns, forming a matrix-like structure. Each element in a 2D array has two indices: one for the row and one for the column. You can access specific elements in a 2D array by specifying both the row and column indices.

Two-dimensional array

Real Life Examples of 1D arrays

1. Imagine that you want to keep a list with all the names of your classmates, for that we can use 1D arrays. (even fruits, objects etc.)

2. If I want to know the ages of all your classmates i can use 1D arrays.

3. If I want to keep a list with all the hobbies of my friends i can use 1D arrays.

Real Life Examples of 2D arrays

1. Imagine that as a teacher I want to place in a classroom my students in a specific order for that I will need to use 2D arrays.

2. If I want to make a grid with the position of every building in GCB for that I will have to use 2D arrays.

3. Imagine that you are playing or have played a board game that uses tiles such as chess, each tile representing a specific location.

1D Array Example in Python

# Creating a 1D array

numbers = [1, 2, 3, 4, 5]

(the number 1 is located in the index 0, number 2 is located in the index 1 etc.)

# Accessing elements in a 1D array

print(numbers[0]) # Output result will be number : 1

print(numbers[2]) # Output result will be number : 3

1D Array Example in PSEUDOCODE

// Declaring a 1D array

DECLARE Numbers : ARRAY[1, 2, 3, 4, 5] OF INTEGER

(the number 1 is located in the index 0, number 2 is located in the index 1 etc.)

// Accessing elements in a 1D array and display them
OUTPUT Numbers[0] // this will display the number 1

OUTPUT Numbers[4] // Output result will be number : 5

2D Array Example in Python

# Creating a 2D array

matrix = [[1, 2, 3],[4, 5, 6],[7, 8, 9]]

# Accessing elements in a 2D array

print(matrix[0][1]) # Output: 2 (row index: 0, column index: 1)

print(matrix[2][0]) # Output: 7 (row index: 2, column index: 0)

​matrix = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]]

Class work 1:

1D arrays

1. Create a 1D array with the name MyList and populate it using a FOR loop in PYTHON

2. Enter these 10 values in order 27, 19, 36, 42, 16, 89, 21, 16, 55, 72

3. Write your python programming code on a piece of paper with your name and grade.

4. Use the example PSEUDOCODE to translate to Python

//declaring a 1D array in Pseudocode with 10 elements
DECLARE MyList : ARRAY[0,9] OF INTEGER

OUTPUT "Enter these 10 values in order 27, 19, 36, 42, 16, 89, 21, 16, 55, 72"
//using a for loop to ask the user to insert 10 different values
FOR Counter ← 0 TO 9
OUTPUT "Enter next value "
INPUT MyList[Counter]
NEXT Counter
OUTPUT MyList[]

​PSEUDOCODE

#DECLARING AN EMPTY 1d ARRAY
Array = []

print("Enter these 10 values in order 27, 19, 36, 42, 16, 89, 21, 16, 55, 72")

#USING A FOR LOOP TO ASK THE USER TO INSERT 4 VALUES
for counter in range(1,10):

number = int(input("Enter your value: "))

Array.append(number)

#DISPLAYING THE NUMBERS OF THE ARRAY

print("My array values are", Array)

print("Index 0 value is: ", Array[0])

PYTHON PROGRAMMING

Class work 2:

2D arrays

Create a 2D array with the name MyTable to store exactly the numbers you can see to the right for each column and row.
Write your python programming code in your notebooks.

PSEUDOCODE Class Work 2

//declaring a 2D array named MyTable
DECLARE MyTable : ARRAY[0:9,0:2] OF INTEGER
//displaying to the user what he/she has to insert
OUTPUT "Enter these values in order 27, 19, 36, 42, 16, 89, 21, 16, 55, 34"
OUTPUT "Enter these values in order 31, 67, 98, 22, 35, 46, 71, 23, 11, 76"
OUTPUT "Enter these values in order 17, 48, 29, 95, 61, 47, 28, 13, 77, 21"
FOR ColumnCounter ← 0 TO 2
FOR RowCounter ← 0 TO 9
OUTPUT "Enter next value "
INPUT MyTable[RowCounter, ColumnCounter]
NEXT RowCounter
NEXT ColumnCounter
//displaying the element at the index [2,1]
OUTPUT MyList[2,1]

PYTHON Class Work 2
WRITING THE DATA BY COLUMN

#declaring a 2D array named MyTable

MyTable = [[],[],[]]

#displaying to the user what he/she has to insert

print("Enter these values in order: 27, 19, 36, 42, 16, 89, 21, 16, 55, 34")

print("Enter these values in order: 31, 67, 98, 22, 35, 46, 71, 23, 11, 76")

print("Enter these values in order: 17, 48, 29, 95, 61, 47, 28, 13, 77, 21")

for RowCounter in range (3):

for ColumnCounter in range (3):

Number = int(input("Enter next value: "))

MyTable[ColumnCounter].append(Number)

print("NEXT COLUMN")

print("NEXT ROW")

print("The value at [2,1] is", MyTable[2][1])

print("The whole array is: ", MyTable)

PYTHON Class Work 2
Writing the data by row

#declaring a 2D array named MyTable

MyTable = [[],[],[]]

#displaying to the user what he/she has to insert

print("Enter these values in order: 27, 19, 36, 42, 16, 89, 21, 16, 55, 34")

print("Enter these values in order: 31, 67, 98, 22, 35, 46, 71, 23, 11, 76")

print("Enter these values in order: 17, 48, 29, 95, 61, 47, 28, 13, 77, 21")

for RowCounter in range (3):

for ColumnCounter in range (3):

Number = int(input("Enter next value: "))

MyTable[ColumnCounter].append(Number)

print("NEXT COLUMN")

print("NEXT ROW")

print("The value at [2,1] is", MyTable[2][1])

print("The whole array is: ", MyTable)

THANK YOU FOR WATCHING AND WORKING