Programming Readiness: Loops, Counters, and Accumulators

This module supports R1, R2, and R6. All work here is formative. Pick Java or Python and stay with it.

Specification checklist

Traced/worked example

To plant as many flowers as possible with no two adjacent, plant from the left and mark each planted plot 1 so the next index sees a neighbor.

int[] bed = {0, 0, 0};
int n = 0;
for (int i = 0; i < bed.length; i++) {
    boolean left = i == 0 || bed[i - 1] == 0;
    boolean right = i == bed.length - 1 || bed[i + 1] == 0;
    if (bed[i] == 0 && left && right) {
        bed[i] = 1;
        n++;
    }
}

Index 0 is planted (n = 1). Index 1 then has a left neighbor, so it is skipped. Index 2 is planted (n = 2). If you forget to write 1 back, every plot still looks empty and n becomes 3.

Practice

Guided: Trace {1, 0, 0, 0, 1} with marking. After each i, write the bed and n.

Independent: Implement countPlantable (mark as you plant) and countOccurrences.

Java: Practice.java, PracticeTest.java

javac Practice.java PracticeTest.java && java PracticeTest

Python: practice.py

python3 practice.py

Copy the array before mutating if you need the original later.

Common mistakes

• Counting a plant without marking the plot.
• Stopping the loop early instead of visiting every index.
• Off-by-one: i <= length.

Exit guidance

Complete the self-check and tests. Explain why {0, 0, 0} plants 2 flowers, not 3.

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