hardDSA

What is a greedy algorithm?

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01

Understand the problem

Explain greedy and when it works.

greedy
02

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04

Read the code

Activity selection (interval scheduling)
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def max_activities(intervals):
    # intervals = list of (start, end)
    intervals.sort(key=lambda x: x[1])   # by finish time
    count, last_end = 0, float('-inf')
    for start, end in intervals:
        if start >= last_end:
            count += 1
            last_end = end
    return count


# --- demo ---
print(max_activities([(1, 3), (2, 5), (4, 7), (6, 9), (8, 10)]))   # 3
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