Students - Unit 6 Review for Assessment - APCS PDF

Unit 6 - Lists, Loops, and Traversals Unit Vocabulary ​ List: an ordered collection of elements ​ Element: an individual value in a list that is assigned a unique index ​ Index: a common method for referencing the elements in a list or string using numbers ​ Iteration: a repetitive porti...

Unit 6 - Lists, Loops, and Traversals Unit Vocabulary ​ List: an ordered collection of elements ​ Element: an individual value in a list that is assigned a unique index ​ Index: a common method for referencing the elements in a list or string using numbers ​ Iteration: a repetitive portion of an algorithm which repeats a specified number of times or until a given condition is met. ​ Infinite loop: occurs when the ending condition will never evaluate to true. ​ Traversal: the process of accessing each item in a list one at a time. ​ Data abstraction: manage complexity in programs by giving a collection of data a name without referencing the specific details of the representation. 1. Lists ​ Definition: A list is a collection of elements stored in a single variable. ​ Key Operations: ○​ appendItem(list, value): Adds a value to the end of a list. ○​ removeItem(list, index): Removes the element at the specified index. ○​ insertItem(list, index, value): Inserts a value at a specific position in the list. ​ Finding Length: Use list.length to find the total number of elements in a list. Example Code: 2. Loops ​ for Loops: Used to iterate a specific number of times. ○​ Syntax: for(var i = 0; i < list.length; i++) ensures the loop runs once for each element in a list.  ​ while Loops: Used when the number of iterations is not predetermined. ○​ Avoid infinite loops by ensuring the condition can evaluate to false. Example Code: Explanation: This results in an infinite loop because count will never equal 5. 3. Traversals ​ Definition: Using loops to visit each element in a list. ​ Filtering Elements: Apply conditions to decide whether to keep or discard elements. Example Code: 4. Boolean Conditions  ​ Controlling Loops and Decisions: ○​ if (condition) checks if a statement is true. ○​ Conditions in loops must eventually evaluate to false to stop the loop. Example Code: 5. Simulations ​ Definition: Programs that model real-world scenarios using loops and conditions. ​ Example: Coin Flip Simulation Key Insight: The total number of heads and tails will always equal the number of flips. 6. Debugging Tips ​ Ensure loops have proper stopping conditions. ​ Always check list indices to avoid going out of bounds. ​ Use print statements (console.log()) to debug and track variable values. Example Questions: Question: What does the following program output?​ ​ Answer: ["air", "rock", "air"] Question: What is the minimum value in the list [15, 20, 22, 23, 1] using this code?​ Answer: 1 Resources for Additional Review & Practice ​ Lesson 1, 2, 3: Lists Explore, Investigate & Practice ​ Lesson 5, 6, 7: Loops Explore, Investigate, & Practice ​ Lesson 9, 10, 11: Traversals Explore, Investigate, & Practice Review these lessons on Code.org to reinforce the key concepts and try coding examples provided in the platform. Grid-Based Traversal Walkthrough This section provides a detailed explanation of how a loop iterates to move a robot through a grid, breaking down each step of its traversal. This topic is relevant for understanding how to solve problems where a program must navigate through a grid to reach a target location. Concepts to Understand 1.​ Robot Movement Commands: ○​ Robots on grids are typically controlled using specific commands such as: ​ moveForward(): Moves the robot one square in the direction it is currently facing. ​ turnLeft() or turnRight(): Changes the direction the robot is facing. 2.​ Grid Coordinates: ○​ A grid can be represented as rows and columns, similar to a 2D array. ○​ For example, the top-left corner is often (0, 0). ○​ Moving down increases the row index, and moving right increases the column index. 3.​ Traversals and Loops: ○​ Loops are used to repeat movements until the robot reaches its goal. ○​ Conditions in loops ensure the robot stops moving once it reaches the target square. Example Problem Scenario: A robot is on a 4x4 grid and starts at (0, 0) facing up. The goal is to move the robot to (2, 3) following a specific path. Path to Follow: 1.​ Move down 2 squares. 2.​ Move right 3 squares. Step-by-Step Solution Code Example: Explanation: 1.​ First Loop (Moving Down): ○​ The robot needs to move 2 squares down, so we use a for loop that runs 2 times. ○​ Each iteration calls moveForward() to move the robot one square. 2.​ Turning Right: ○​ Once the robot is at (2, 0), it turns right to face the correct direction for moving horizontally. 3.​ Second Loop (Moving Right): ○​ The robot needs to move 3 squares to the right, so we use another for loop that runs 3 times. ○​ Each iteration calls moveForward() to move one square right. Visual Representation Initial Grid Position: R............... ​ R represents the robot at (0, 0), facing up. After First Loop (Move Down 2):.... R........... After Turning Right:.... R... (facing right)........ After Second Loop (Move Right 3):.......R........ Common Mistakes to Avoid 1.​ Incorrect Loop Conditions: ○​ Ensure the number of iterations matches the required movements. ○​ Example: Using i