5/17 每日一題(26進位)

 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"].

class Solution:

    def titleToNumber(self, columnTitle: str) -> int:

        #chr(65)="A"

        #ord("A")=65

        n=len(columnTitle)-1 #最高位數次方 (例如200=2*[10**2],len(200)=3)

        point=0

        for i in columnTitle:

            x=26**n

            a=ord(i)-64

            point += a*x  #(ex:201=2*10**2 + 0*10**1 + 2*10**0)

            n -= 1

        return point

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