Description
Given a string columnTitle that represents the column title as appears in an Excel sheet, return its corresponding column number.
For example:
A -> 1 B -> 2 C -> 3 ... Z -> 26 AA -> 27 AB -> 28 ...
Examples:
Example 1:
Input: columnTitle = "A"
Output: 1
Example 2:
Input: columnTitle = "AB"
Output: 28
Example 3:
Input: columnTitle = "ZY"
Output: 701Solution in Python
Python
class Solution:
def titleToNumber(self, columnTitle: str) -> int:
# Initialize the result to 0
result = 0
# Iterate over each character in the string
for char in columnTitle:
# Convert the character to its corresponding value (A -> 1, B -> 2, ..., Z -> 26)
# ord('A') gives 65, so ord(char) - ord('A') + 1 gives the correct value
char_value = ord(char) - ord('A') + 1
# Update the result by shifting previous result by 26 (like base-26) and adding current character's value
result = result * 26 + char_value
# Return the final result which is the column number
return resultExplanation:
- Initial Setup:
resultis initialized to 0. This variable will hold the cumulative value as we process each character in thecolumnTitlestring.
- Iteration through Characters:
- The code loops through each character in the
columnTitle. For each character, it calculates its corresponding value:ord(char) - ord('A') + 1is used to convert the character to its respective column number. For example, ‘A’ becomes 1, ‘B’ becomes 2, and so on up to ‘Z’, which becomes 26.
- The code loops through each character in the
- Updating the Result:
- The result is updated by treating it as a number in a base-26 numeral system. For each character, the current result is multiplied by 26 (to shift it one place to the left in base-26) and then the value of the current character is added to it. This process effectively accumulates the final column number.
- Return the Result:
- After processing all the characters, the final value in
resultis returned, which represents the column number corresponding to the input title.
- After processing all the characters, the final value in
This code handles all cases within the constraints, including single-letter titles and titles with multiple characters.
Solution in Javascript
JavaScript
/**
* @param {string} columnTitle
* @return {number}
*/
var titleToNumber = function(columnTitle) {
// Initialize the result variable to 0
let result = 0;
// Iterate over each character in the columnTitle string
for (let i = 0; i < columnTitle.length; i++) {
// Get the current character
let char = columnTitle[i];
// Convert the character to its corresponding value (A -> 1, B -> 2, ..., Z -> 26)
// charCodeAt(0) gets the ASCII value of the character, and subtracting 64 adjusts it to A=1, B=2, ..., Z=26
let charValue = char.charCodeAt(0) - 'A'.charCodeAt(0) + 1;
// Update the result by shifting previous result by 26 (like base-26) and adding current character's value
result = result * 26 + charValue;
}
// Return the final result which is the column number
return result;
};Solution in Java
Java
class Solution {
public int titleToNumber(String columnTitle) {
// Initialize the result variable to 0
int result = 0;
// Iterate over each character in the columnTitle string
for (int i = 0; i < columnTitle.length(); i++) {
// Get the current character
char currentChar = columnTitle.charAt(i);
// Convert the character to its corresponding value (A -> 1, B -> 2, ..., Z -> 26)
// 'A' is 65 in ASCII, so currentChar - 'A' + 1 gives the correct value
int charValue = currentChar - 'A' + 1;
// Update the result by shifting previous result by 26 (like base-26) and adding current character's value
result = result * 26 + charValue;
}
// Return the final result which is the column number
return result;
}
}Solution in C#
C#
public class Solution {
public int TitleToNumber(string columnTitle) {
// Initialize the result variable to 0
int result = 0;
// Iterate over each character in the columnTitle string
for (int i = 0; i < columnTitle.Length; i++) {
// Get the current character
char currentChar = columnTitle[i];
// Convert the character to its corresponding value (A -> 1, B -> 2, ..., Z -> 26)
// 'A' has an ASCII value of 65, so currentChar - 'A' + 1 gives the correct value
int charValue = currentChar - 'A' + 1;
// Update the result by shifting the previous result by 26 (like base-26) and adding the current character's value
result = result * 26 + charValue;
}
// Return the final result which is the column number
return result;
}
}