Given a column title as appear 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: “A”
Output: 1Example 2:
Input: “AB”
Output: 28Example 3:
Input: “ZY”
Output: 701Constraints:
1 <= s.length <= 7
s consists only of uppercase English letters.
s is between “A” and “FXSHRXW”.
Compute the Excel Sheet Column Number using Python Iterative Function
The following is a simple Python function that takes a column title, and compute the base-26 numeric values. As the number starts from 1, we have to shift the value by one.
1 2 3 4 5 6 | class Solution: def titleToNumber(self, s: str) -> int: ans = 0 for i in s: ans = ans * 26 + ord(i) - 64 return ans |
class Solution: def titleToNumber(self, s: str) -> int: ans = 0 for i in s: ans = ans * 26 + ord(i) - 64 return ans
The runtime complexity is O(N) where N is the length of the string – given the length is 7 we can also say the complexity is O(1). The space requirement is O(1) constant.
The C++ implementation and to convert backwards from the column numbers to excel titles: Excel Sheet Column Number and Title Conversion in C++
See also: Teaching Kids Programming – Converting Spreadsheet Column Titles to Number
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