Kimi K3とオンラインでチャット

def merge_intervals(intervals):
    """Merge overlapping intervals. Each interval is [start, end]."""
    merged = []
    for start, end in sorted(intervals):
        if merged and start <= merged[-1][1]:
            merged[-1][1] = max(merged[-1][1], end)
        else:
            merged.append([start, end])
    return merged


def test_merge_intervals():
    # Overlapping and disjoint intervals
    assert merge_intervals([[1, 3], [2, 6], [8, 10], [15, 18]]) == [[1, 6], [8, 10], [15, 18]]
    # Touching intervals merge; unsorted input handled
    assert merge_intervals([[5, 7], [1, 4], [4, 5]]) == [[1, 7]]
    # Empty and single-interval edge cases
    assert merge_intervals([]) == [] and merge_intervals([[2, 3]]) == [[2, 3]]


test_merge_intervals()
print("All tests passed.")

The function sorts intervals by start time, then walks through once, extending the last merged interval when there's overlap. Runs in O(n log n) time.