Arrays

📊 Array Algorithms

Part 1 of 7 — Searching, Shifting, and Array Manipulation

Linear Search

public int linearSearch(int[] arr, int target) {
    for (int i = 0; i < arr.length; i++) {
        if (arr[i] == target) {
            return i;  // Return index of target
        }
    }
    return -1;  // Not found
}

Shifting Elements

Removing an Element (Shift Left)

// Remove element at index 2 from {10, 20, 30, 40, 50}
// Shift elements left to fill the gap
for (int i = 2; i < arr.length - 1; i++) {
    arr[i] = arr[i + 1];
}
// Result: {10, 20, 40, 50, 50}
// Note: array size unchanged; last element duplicated

Inserting an Element (Shift Right)

// Insert 25 at index 2 in {10, 20, 30, 40, 50}
// Shift elements right first (start from end!)
for (int i = arr.length - 1; i > 2; i--) {
    arr[i] = arr[i - 1];
}
arr[2] = 25;
// Result: {10, 20, 25, 30, 40}
// Note: last element (50) is lost

🔑 Shifting direction matters! Shift LEFT = go forward. Shift RIGHT = go backward to avoid overwriting.

Concept Check 🎯

Reversing an Array

public void reverse(int[] arr) {
    for (int i = 0; i < arr.length / 2; i++) {
        int temp = arr[i];
        arr[i] = arr[arr.length - 1 - i];
        arr[arr.length - 1 - i] = temp;
    }
}

Key insight: Only loop through half the array. Swap element i with element (length - 1 - i).

Consecutive Pairs

// Check if any consecutive elements are equal
public boolean hasConsecutiveDuplicates(int[] arr) {
    for (int i = 0; i < arr.length - 1; i++) {
        if (arr[i] == arr[i + 1]) {
            return true;
        }
    }
    return false;
}

⚠️ Loop to arr.length - 1 (not arr.length) when comparing arr[i] with arr[i + 1] to avoid ArrayIndexOutOfBoundsException.

Selection Sort (AP Exam Reference)

for (int i = 0; i < arr.length - 1; i++) {
    int minIdx = i;
    for (int j = i + 1; j < arr.length; j++) {
        if (arr[j] < arr[minIdx]) {
            minIdx = j;
        }
    }
    // Swap arr[i] and arr[minIdx]
    int temp = arr[i];
    arr[i] = arr[minIdx];
    arr[minIdx] = temp;
}

Applied Recall ✍️

1. Linear search checks each element one by one and has worst-case complexity of _______ comparisons for an array of n elements.

2. When comparing consecutive pairs arr[i] and arr[i+1], the loop should run to arr.length - _______.

3. To swap two values, you need a _______ variable to hold one value temporarily.

Choose the Algorithm 🔍

AP Exam Strategy: Array Algorithms

• Linear search returns -1 for not found — check the return value in conditionals
• Shifting arrays is a very common FRQ task — know both left and right shifts
• When shifting RIGHT, start from the END to avoid overwriting
• Reversing only needs length/2 iterations — do not double-swap!
• Know how to write a swap using a temp variable — this is fundamental
• Selection sort and insertion sort are on the AP quick reference — know how they work

AP-Style Application 🎯

💻 Array Algorithms

Part 2 of 7 — Key Processes

Understanding the processes related to Array Algorithms helps explain how and why patterns develop. This part explores the mechanisms driving key phenomena.

Key Concepts

Concept Check 🎯

Key Processes — Deeper Dive

Process 1

The primary mechanism that drives patterns in Array Algorithms. Understanding this concept is essential for mastering Array Algorithms in AP Computer Science A.

Process 2

A secondary process that shapes outcomes in Array Algorithms. This builds on the previous concept and connects to broader themes in the course.

Cause and effect

The relationship between actions and outcomes in Array Algorithms. This is frequently tested on the AP exam and connects to multiple units in the curriculum.

Applied Recall (exact term answers) ✍️

1. What term refers to the primary mechanism that drives patterns in Array Algorithms?

2. What concept describes a secondary process that shapes outcomes in Array Algorithms?

💻 Array Algorithms

Part 3 of 7 — Patterns & Examples

This part examines specific patterns and real-world examples related to Array Algorithms. Case studies help illustrate abstract concepts.

Key Concepts

Concept Check 🎯

Patterns & Examples — Deeper Dive

Spatial pattern

The geographic distribution related to Array Algorithms. Understanding this concept is essential for mastering Array Algorithms in AP Computer Science A.

Case study

A specific real-world example that illustrates Array Algorithms. This builds on the previous concept and connects to broader themes in the course.

Comparison

Analyzing similarities and differences across examples of Array Algorithms. This is frequently tested on the AP exam and connects to multiple units in the curriculum.

Applied Recall (exact term answers) ✍️

1. What term refers to the geographic distribution related to Array Algorithms?

💻 Array Algorithms

Part 4 of 7 — Connections & Interactions

Array Algorithms connects to other topics in AP Computer Science A. Understanding these connections reveals how different processes interact.

Key Concepts

Concept Check 🎯

Connections & Interactions — Deeper Dive

Interconnection

How Array Algorithms links to other course topics. Understanding this concept is essential for mastering Array Algorithms in AP Computer Science A.

Scale interaction

How Array Algorithms operates differently at local, national, and global scales. This builds on the previous concept and connects to broader themes in the course.

Feedback loop

How outcomes of Array Algorithms can reinforce or modify the original process. This is frequently tested on the AP exam and connects to multiple units in the curriculum.

Applied Recall (exact term answers) ✍️

1. What term refers to how Array Algorithms links to other course topics?

💻 Array Algorithms

Part 5 of 7 — Change Over Time

Array Algorithms has evolved over time. Understanding historical and contemporary changes helps explain current patterns and predict future trends.

Key Concepts

Concept Check 🎯

Change Over Time — Deeper Dive

Continuity

Aspects of Array Algorithms that have remained stable over time. Understanding this concept is essential for mastering Array Algorithms in AP Computer Science A.

Change

How Array Algorithms has transformed due to new forces and conditions. This builds on the previous concept and connects to broader themes in the course.

Trend

The direction of change in Array Algorithms over time. This is frequently tested on the AP exam and connects to multiple units in the curriculum.

Applied Recall (exact term answers) ✍️

1. What term refers to aspects of Array Algorithms that have remained stable over time?

2. What concept describes how Array Algorithms has transformed due to new forces and conditions?

💻 Array Algorithms

Part 6 of 7 — Problem-Solving Workshop

Apply Array Algorithms concepts to data interpretation and analytical scenarios. Practice the types of questions seen on the AP exam.

Key Concepts

Concept Check 🎯

Problem-Solving Workshop — Deeper Dive

Data interpretation

Analyzing maps, graphs, and tables related to Array Algorithms. Understanding this concept is essential for mastering Array Algorithms in AP Computer Science A.

Argumentation

Making evidence-based claims about Array Algorithms. This builds on the previous concept and connects to broader themes in the course.

Spatial reasoning

Using geographic thinking to analyze Array Algorithms. This is frequently tested on the AP exam and connects to multiple units in the curriculum.

Applied Recall (exact term answers) ✍️

1. What term refers to analyzing maps, graphs, and tables related to Array Algorithms?

💻 Array Algorithms

Part 7 of 7 — AP Review

Comprehensive review of Array Algorithms for the AP exam. Focus on key concepts, common question types, and exam strategies.

Key Concepts

Concept Check 🎯

AP Review — Deeper Dive

Key vocabulary

Essential terms and definitions for Array Algorithms. Understanding this concept is essential for mastering Array Algorithms in AP Computer Science A.

Common question types

The most frequent ways Array Algorithms is tested on the AP exam. This builds on the previous concept and connects to broader themes in the course.

Exam strategy

Approaches for answering Array Algorithms questions effectively. This is frequently tested on the AP exam and connects to multiple units in the curriculum.

Applied Recall (exact term answers) ✍️

1. What term refers to essential terms and definitions for Array Algorithms?

2. What concept describes the most frequent ways Array Algorithms is tested on the AP exam?