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Problem solution · Python

Design Excel Sum Formula

Design Excel Sum Formula: a Python solution using direct simulation. Learn the idea, check the complexity, and read the full code, with credit to walkccc LeetCode Solutions.

Technique
Direct simulation
Source
walkccc LeetCode Solutions
Length
51 lines
Start with the idea.

Try the problem first. If you get stuck, read the approach below, then write your own solution. The full code is at the bottom.

Approach

Direct simulation

For Design Excel Sum Formula, the implementation follows the problem’s operations directly while maintaining only the state needed for the next decision.

  1. Translate each rule into one explicit state update.
  2. Maintain the invariant after every processed item.
  3. Return the accumulated state once all relevant input has been handled.

Code notes

  • 51 lines of Python from the credited upstream file 631.py.
  • The implementation visibly relies on sequence storage, hash lookup, ordered lookup.
  • No explicit loop blocks detected.

Complexity

Count the number and nesting of passes over the input, then include the maintained containers in the memory estimate.

Check the problem constraints before deciding whether this complexity will pass.

Source

Code and credit

This code comes from walkccc LeetCode Solutions by P.-Y. Chen (walkccc) and is used under the MIT licence.

Open problem ↗Original source ↗
Full codeDesign Excel Sum Formula · PythonPython
Use this to learn the idea, then write your own version.
from dataclasses import dataclass  @dataclassclass Cell:  val: int = 0  posCount: dict[tuple[int, int], int] | None = None  class Excel:  def __init__(self, height: int, width: str):    self.width = ord(width) - ord('A') + 1    self.sheet = [[Cell() for _ in range(self.width)] for _ in range(height)]   def set(self, row: int, column: str, val: int) -> None:    self._getCell(row, column).val = val    self._getCell(row, column).posCount = {}   def get(self, row: int, column: str) -> int:    cell = self._getCell(row, column)    if not cell.posCount:      return cell.val    val = 0    for pos, count in cell.posCount.items():      val += self.get(pos // self.width + 1, chr(pos %                      self.width + ord('A'))) * count    return val   def sum(self, row: int, column: str, numbers: list[str]) -> int:    self._getCell(row, column).posCount = self._parse(numbers)    return self.get(row, column)   def _getCell(self, row: int, column: str) -> Cell:    return self.sheet[row - 1][ord(column) - ord('A')]   def _parse(self, numbers: list[str]) -> dict[int, int]:    count: dict[int, int] = {}    for s in numbers:      startRow, startCol, endRow, endCol = self._parseRange(s)      for i in range(startRow - 1, endRow):        for j in range(ord(startCol) - ord('A'), ord(endCol) - ord('A') + 1):          pos = i * self.width + j          count[pos] = count.get(pos, 0) + 1    return count   def _parseRange(self, s: str) -> tuple[int, str, int, str]:    if ':' not in s:      return int(s[1:]), s[0], int(s[1:]), s[0]    l, r = s.split(':')    return int(l[1:]), l[0], int(r[1:]), r[0]

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