168. excel table column name

168. Excel Table column name

Original title link ：https://leetcode.cn/problems/excel-sheet-column-title/

Give you an integer columnNumber , Back to it in Excel The name of the corresponding column in the table .

for example ：

A -> 1
B -> 2
C -> 3
…
Z -> 26
AA -> 27
AB -> 28
…

Example 1：

Input ：columnNumber = 1
Output ：“A”
Example 2：

Input ：columnNumber = 28
Output ：“AB”
Example 3：

Input ：columnNumber = 701
Output ：“ZY”
Example 4：

Input ：columnNumber = 2147483647
Output ：“FXSHRXW”

Their thinking ：

Calculate the corresponding letter from low to high by calculating the remainder and quotient , here 26 The radix calculation is 0 To 25 This 26 Number , but A It's from 1 At the beginning , So when calculating the remainder and quotient , In order to be able to communicate with 26 The base number remains the same , So subtract it first 1, Calculate again .

Code implementation ：

class Solution:
    def convertToTitle(self, columnNumber: int) -> str:
      ans = []
      while columnNumber > 0:
          #  the reason being that 26 Base number ：0~25, but A It's from 1 At the beginning , So the letters are relative to the normal 26 Decimal digit 
          #  Added one more 1, So it's using 26 In hexadecimal calculation , First subtract 1 individual 1
          columnNumber -= 1
          #  Calculate the remainder , The rightmost letter 
          cur = columnNumber % 26
          #  Convert letters 
          cur_ans = chr(cur + ord('A'))
          ans.insert(0, cur_ans)

          #  Seeking quotient , Calculate the next letter 
          columnNumber //= 26

      return ''.join(ans)

reference ：
https://leetcode.cn/problems/excel-sheet-column-title/solution/excelbiao-lie-ming-cheng-by-leetcode-sol-hgj4/