Excel Cell Calculation

Design an Excel-like spreadsheet class supporting set/get operations and dependency-aware formulas. One canonical variant stores sums over cells and ranges; another accepts basic arithmetic formulas between two referenced cells in a fixed 26-by-100 sheet. Examples Example 1: Input: ["Excel", "set", "sum", "set", "get"] [[3, "C"], [1, "A", 2], [3, "C", ["A1", "A1:B2"]], [2, "B", 2], [3, "C"]] Output: [null, null, 4, null, 6] Explanation: The formula in C3 counts A1 once directly and once through the range A1:B2. Updating B2 later changes the formula result from 4 to 6. Constraints 1 <= height <= 26 A <= width <= Z 1 <= row <= height A <= column <= width -100 <= val <= 100 1 <= numbers.length <= 5 Each formula reference is either a single cell or a valid rectangular range. At most 100 calls will be made to set, get, and sum. The input will not create circular formula dependencies. Notes Alternate canonical variant — basic arithmetic formulas Initialize a spreadsheet with 26 columns and 100 rows; every cell starts empty. setCell accepts a literal string, a number, or a formula. getCell returns the current value of a cell. A helper such as parseFormula may parse formulas. Any string beginning with = is a valid formula. Only +, -, *, and / between two cell references are required, such as =B1-B2 or =A1+A2. Inputs and formulas are valid, so input validation is out of scope. When either referenced cell changes, every dependent formula value must update accordingly.