How-to Intermediate

Chapter 1 Updated April 21, 2026

My Calendar I

Overlap test per booking: start < existing_end AND end > existing_start.

Full 5m
Revision 2m
Flow 1m

LeetCode #729 — one-liner.

Implement book(start, end) that returns true if the new half-open event can be added without overlapping any existing booking, otherwise false.

Half-open overlap check.

Overlap formula: start < existing_end AND end > existing_start (strict <, > because [start, end) is half-open).
Linear scan over existing bookings per call. BST / SortedList optimisation brings per-call to O(log n).

Seven lines.

class MyCalendar:
    def __init__(self): self.bookings = []
    def book(self, start, end):
        for s, e in self.bookings:
            if start < e and end > s:
                return False
        self.bookings.append((start, end))
        return True

Per-call cost.

Time per book O(n) with a list; O(log n) with a balanced BST / SortedList.
Space O(n) — stores all accepted bookings.

One to remember.

Adjacent half-open events [10, 20) + [20, 30) — no overlap (20 < 20 is false). That’s the point of half-open semantics.

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