171-Excel Sheet Column Number

100-Same Tree | Links:

题意

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: 1

Example 2:

• Input: “AB”
• Output: 28

Example 3:

• Input: “ZY”
• Output: 701

Constraints:

• 1 <= s.length <= 7
• s consists only of uppercase English letters.
• s is between “A” and “FXSHRXW”.

思路

• 字母的26进制转换

class Solution(object):
    def titleToNumber(self, s):
        """
        :type s: str
        :rtype: int
        """
        res = 0
        for c in s:
            res *= 26
            res += ord(c) - ord('A') + 1
        return res        

分析

• Time: O(n)
• Space: O(1)