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To solve this problem, we use a mathematical approach similar to converting a number to a different base. Here, the base is 26, similar to the English alphabet, where each letter corresponds to a unique representation of a number. This approach involves repeated division by 26 and mapping the remainder to the corresponding letter in the alphabet.
Time Complexity: O(log26(n)), where n is the columnNumber, due to repeated division by 26.
Space Complexity: O(log26(n)), to store the result string.
1def convert_to_title(column_number: int) -> str:
2 result = []
3 while column_number > 0:
4 column_number -= 1
5 result.append(chr((column_number % 26) + ord('A')))
6 column_number //= 26
7 return ''.join(reversed(result))
8
9print(convert_to_title(28)) # Output: ABIn Python, we use a list to store characters and later join them into a string. We map the remainder of the division to corresponding characters using chr and ord.
This approach uses recursion to solve the problem. The function calls itself with the quotient of the column number divided by 26, constructing the result string backwards using the modulo operation to index into the alphabet.
Time Complexity: O(log26(n))
Space Complexity: O(log26(n)), due to the recursive call stack.
1using System;
public class ExcelConverter {
public string ConvertToTitle(int columnNumber) {
if (columnNumber <= 0) return string.Empty;
columnNumber--;
return ConvertToTitle(columnNumber / 26) + (char)((columnNumber % 26) + 'A');
}
public static void Main(){
ExcelConverter ec = new ExcelConverter();
Console.WriteLine(ec.ConvertToTitle(28)); // Output: AB
}
}C# uses recursion to dynamically build the Excel title by breaking down the problem into smaller subproblems, with character values calculated and appended upon exit from each recursion level.