Teaching Kids Programming: Videos on Data Structures and Algorithms
Spreadsheets often use this alphabetical encoding for its columns: “A”, “B”, “C”, …, “AA”, “AB”, “AC”, …, “ZZ”, “AAA”, “AAB”, “AAC”, …. Given a string s representing an alphabetical column id, return its column number. For example, given “A”, return 1. Given “AA”, return 27.
Example 1
Input
s = “AA”
Output
27
Multiply by Base
Like converting other base numbers to decimals, we can multiply the current answer by base iteratedly and add the new value.
class Solution:
def excelColumnTitleToDecimal(self, s):
a = 0
for i in s:
a = a * 26 + (ord(i) - 65 + 1)
return a
The Excel/Spreadsheet starts with one instead or zero, thus we have to add one during conversion. The time complexity is O(N).
–EOF (The Ultimate Computing & Technology Blog) —
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