Arrays

邊玩邊學

回答這些題目賺取能量，接著就能釣魚、探索。不需要帳號。

給教育者： 為 Arrays（Computer Science、CIE）準備好可直接使用的課程投影片, 複習筆記——用於你的課程，或把這個主題當成互動班級活動，讓學習者以即時遊戲的方式進行。

課程筆記

1-Dimensional Arrays

  • An array is an ordered, static set of elements stored in a fixed-size memory location.
  • An array can only store one data type (e.g., all integers or all strings).
  • In CIE pseudocode, indexing starts at 1; in Python, indexing starts at 0 (zero-indexed).
  • Declare a 1D array in pseudocode: `DECLARE scores: ARRAY[1:5] OF INTEGER` creates an array with 5 elements (indices 1–5).
  • Assign a value: `scores[4] ← "Red"` (pseudocode) or `scores[4] = "Red"` (Python).
  • Access an element: `MyArray[1]` (pseudocode) or `array[0]` (Python).
  • Modify an element: `MyArray[index] ← newValue` (pseudocode) or `array[index] = newValue` (Python).
  • Use `len(array)` in Python to get array length; pseudocode requires storing the length in a variable.

An array is an ordered collection of same-type values stored under one name and reached by index.

An array is an ordered collection of same-type values stored under one name and reached by index.

2-Dimensional Arrays

  • A 2D array extends a 1D array by adding another dimension, visualised as a table with rows and columns.
  • In pseudocode, declare: `DECLARE arr: ARRAY[1:3, 1:2] OF STRING` (3 rows, 2 columns).
  • In Python, initialise as a list of lists: `arr = [["Alice", 25], ["Bob", 30]]`.
  • Access an element: `arr[row, col]` (pseudocode) or `arr[row][col]` (Python).
  • Assign a value: `players[3,1] ← "Holly"` (pseudocode) or `players[2][0] = "Holly"` (Python).
  • Iterate using nested loops: outer loop for rows, inner loop for columns.
  • Examiner tip: Always check the question's example to see whether the order is `[row][col]` or `[col][row]`.

Common Operations on Arrays

  • Iterating over a 1D array: use a single `FOR` loop from 1 to length (pseudocode) or `for element in array:` (Python).
  • Iterating over a 2D array: use nested `FOR` loops (pseudocode) or nested `for` loops (Python).
  • Length of a 1D array: in Python, `len(array)`; in pseudocode, store the declared size in a variable.
  • Modifying elements: assign a new value to a specific index.
  • Accessing elements: use the index (starting at 1 in pseudocode, 0 in Python).

Traversal visits each indexed cell in turn, from the first index to the last.

Traversal visits each indexed cell in turn, from the first index to the last.

Pseudocode vs Python Syntax

  • Declaration: `DECLARE arr: ARRAY[1:5] OF INTEGER` (pseudocode) vs `arr = [0]×5` or `arr = []` (Python).
  • Indexing: pseudocode uses `arr[1]` for first element; Python uses `arr[0]`.
  • Assignment: `arr[1] ← 10` (pseudocode) vs `arr[0] = 10` (Python).
  • 2D indexing: `arr[1,2]` (pseudocode) vs `arr[0][1]` (Python).
  • Iteration: `FOR i ← 1 TO 5` (pseudocode) vs `for i in range(5):` (Python).

Worked Example: 2D Array Access

  • Given a 2D array `minsWatched` with rows (days) and columns (children), access specific values.
  • Example: `minsWatched[0][3]` gives Elias's minutes on Monday (row 0, col 3).
  • To output Lyla's minutes on Tuesday: `print(minsWatched[1][1])` (row 1, col 1).
  • To output Harry's minutes on Friday: `print(minsWatched[4][2])` (row 4, col 2).
  • To output Quinn's minutes on Wednesday: `print(minsWatched[2][0])` (row 2, col 0).

投影片

Sign up free to view the lesson slides

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

免費註冊登入

練習題

免費預覽——59 題中的 8 題。註冊即可查看全部。

  1. 1.What is an array?

    Easy
    • AAn ordered, static set of elements in a fixed-size memory location
    • BAn unordered collection of elements that can change size dynamically
    • CA single variable that stores multiple data types
    • DA data structure that can only store characters

  2. 2.In CIE pseudocode, what is the starting index of an array?

    Easy
    • A0
    • B1
    • CDepends on the programming language
    • DThe index is always specified by the programmer

  3. 3.Which of the following correctly declares a 1D array in CIE pseudocode?

    Easy
    • ADECLARE scores: ARRAY[1:5] OF INTEGER
    • BDECLARE scores: ARRAY[0:4] OF INTEGER
    • Cscores = [1,2,3,4,5]
    • DARRAY scores[5]

  4. 4.What does the following CIE pseudocode output? DECLARE MyArray : ARRAY[1:3] OF INTEGER MyArray[1] ← 5 MyArray[2] ← 10 MyArray[3] ← 15 OUTPUT MyArray[2]

    Easy
    • A5
    • B10
    • C15
    • DError

  5. 5.A 2D array is declared as DECLARE table: ARRAY[1:4, 1:3] OF INTEGER. How many elements does it contain?

    Easy
    • A7
    • B12
    • C4
    • D3

  6. 6.In CIE pseudocode, what is the correct way to assign the value 'Red' to the fourth element of a 1D array called colours?

    Easy
    • Acolours[4] ← 'Red'
    • Bcolours[3] ← 'Red'
    • Ccolours[4] = 'Red'
    • Dcolours[0] ← 'Red'

  7. 7.Consider the following 2D array in CIE pseudocode: DECLARE grid : ARRAY[1:2, 1:2] OF INTEGER grid[1,1] ← 1 grid[1,2] ← 2 grid[2,1] ← 3 grid[2,2] ← 4 What is the value of grid[2,1]?

    Easy
    • A1
    • B2
    • C3
    • D4

  8. 8.In CIE pseudocode, which loop structure is typically used to iterate through all elements of a 1D array?

    Easy
    • AFOR...NEXT loop
    • BWHILE loop
    • CREPEAT...UNTIL loop
    • DIF...THEN statement

Unlock all 59 questions & more

建立免費帳號，即可查看這個主題的所有題目、投影片、字卡與複習筆記。

免費註冊登入

歷屆試題

這個主題的歷屆試題練習即將推出。
即將推出