File: cells-in-a-range-on-an-excel-sheet/solution.py

Date: 2026-06-06

Time: 15:33

cells-in-a-range-on-an-excel-sheet/solution.py

Purpose

This file solves LeetCode 2194 — Cells in a Range on an Excel Sheet. It owns exactly one responsibility: given a range string like "K1:L2", enumerate every cell in that rectangular region in column-major then row-major order.

Key Components

cell_range(s: str) -> list[str] — The sole public function. Accepts a 5-character range string in the format "<col1><row1>:<col2><row2>" and returns a flat list of cell identifiers.

Contract:

• Input s is exactly 5 characters: a letter, a digit, a colon, a letter, a digit.
• Output is sorted by column first (lexicographic on the letter), then by row (numeric on the digit) within each column.

Patterns

Direct index parsing — Rather than using regex or split(":"), the function destructures the string by position (s[0], s[1], s[3], s[4]), skipping the colon at s[2]. This works because the input format is fixed-width.

ord/chr column iteration — Columns are letters, so the code converts to ordinals to use range(), then converts back with chr(). This is the standard Python idiom for iterating over a contiguous range of characters.

Nested list comprehension — The outer loop iterates columns, the inner loop iterates rows. This ordering naturally produces the required column-major sort without a separate sort step.

Dependencies

Imports: None — pure stdlib, no external dependencies.

Imported by: The testsolution.py in the same directory. The massive "Imported By" list in the prompt is misleading — that appears to be an artifact of the test harness sharing a common test runner pattern, not actual imports of cellrange from hundreds of unrelated test files.

Flow

1. Parse s into four components: c1 (start column letter), r1 (start row int), c2 (end column letter), r2 (end row int).

2. Outer loop: iterate column ordinals from ord(c1) to ord(c2) inclusive.

3. Inner loop: iterate row numbers from r1 to r2 inclusive.

4. For each (column, row) pair, produce an f-string "{chr(c)}{r}".

5. Return the collected list.

For input "A1:C2", execution produces: ["A1", "A2", "B1", "B2", "C1", "C2"].

Invariants

• Fixed-width input: The parsing assumes s is always exactly "X#:Y#" — single-letter columns, single-digit rows. This matches the LeetCode constraint (columns A-Z, rows 1-9).
• Column ordering: c1 <= c2 and r1 <= r2 are assumed (guaranteed by the problem). If violated, range() returns empty and the function returns [].
• Output ordering: Column-major order is enforced structurally by nesting — no post-hoc sort needed.

Error Handling

None. The function trusts its caller to provide well-formed input per the LeetCode spec. Out-of-spec input (multi-letter columns, multi-digit rows, malformed strings) would produce IndexError or incorrect results silently.