LeetCode 0171. Excel Sheet Column Number Solution in Java, Python, C++, JavaScript, Go & Rust | Explanation + Code

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 
...

 

Example 1:

Input: columnTitle = "A"
Output: 1

Example 2:

Input: columnTitle = "AB"
Output: 28

Example 3:

Input: columnTitle = "ZY"
Output: 701

 

Constraints:

• 1 <= columnTitle.length <= 7
• columnTitle consists only of uppercase English letters.
• columnTitle is in the range ["A", "FXSHRXW"].

Solutions

Solution 1: Base Conversion

The column name in Excel is a representation in base 26. For example, "AB" represents the column number 1 × 26 + 2 = 28.

Therefore, we can iterate through the string columnTitle, convert each character to its corresponding value, and then calculate the result.

The time complexity is O(n), where n is the length of the string columnTitle. The space complexity is O(1).

PythonJavaC++GoTypeScriptC#

class Solution: def titleToNumber(self, columnTitle: str) -> int: ans = 0 for c in map(ord, columnTitle): ans = ans * 26 + c - ord("A") + 1 return ans(code-box)

class Solution { public int titleToNumber(String columnTitle) { int ans = 0; for (int i = 0; i < columnTitle.length(); ++i) { ans = ans * 26 + (columnTitle.charAt(i) - 'A' + 1); } return ans; } }(code-box)

class Solution { public: int titleToNumber(string columnTitle) { int ans = 0; for (char& c : columnTitle) { ans = ans * 26 + (c - 'A' + 1); } return ans; } };(code-box)

func titleToNumber(columnTitle string) (ans int) { for _, c := range columnTitle { ans = ans*26 + int(c-'A'+1) } return }(code-box)

function titleToNumber(columnTitle: string): number { let ans: number = 0; for (const c of columnTitle) { ans = ans * 26 + (c.charCodeAt(0) - 'A'.charCodeAt(0) + 1); } return ans; }(code-box)

public class Solution { public int TitleToNumber(string columnTitle) { int ans = 0; foreach (char c in columnTitle) { ans = ans * 26 + c - 'A' + 1; } return ans; } }(code-box)