Excel Sheet Column Number Explained

Problem Statement

Given a string s representing an Excel column title (e.g., "A", "AB", "ZY"), return its corresponding column number. This is the reverse of converting a number to a title, treating the title as a base-26 number where A=1, B=2, ..., Z=26. This problem tests your ability to parse strings and perform base conversion.

Example

Input: s = "AB"

Output: 28

Explanation: AB = 1*26^1 + 2*26^0 = 26 + 2 = 28.

Code

public class Solution {
    public int titleToNumber(String s) {
        int result = 0;
        for (char c : s.toCharArray()) {
            result *= 26;
            result += (c - 'A' + 1);
        }
        return result;
    }

    public static void main(String[] args) {
        Solution sol = new Solution();
        System.out.println(sol.titleToNumber("AB")); // 28
    }
}
            

def title_to_number(s):
    result = 0
    for char in s:
        result *= 26
        result += ord(char) - ord('A') + 1
    return result

# Example usage
print(title_to_number("AB"))  # 28
            

function titleToNumber(s) {
    let result = 0;
    for (let char of s) {
        result *= 26;
        result += char.charCodeAt(0) - 'A'.charCodeAt(0) + 1;
    }
    return result;
}

// Example usage
console.log(titleToNumber("AB")); // 28
            

Explanation

• Treat the string as a base-26 number, where each letter represents a digit.
• For each character, multiply the current result by 26 (shift left in base-26).
• Add the value of the current letter (A=1, B=2, ..., Z=26).
• Continue until all characters are processed.
• Return the final number.

Note