Question
Formatted question description: https://leetcode.ca/all/171.html
171 Excel Sheet Column Number
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 (26*26+25)
Algorithm
It is equivalent to a problem of converting from hexadecimal to decimal. It is not difficult, as long as the conversion is bit by bit.
Code
Java
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public class Excel_Sheet_Column_Number { class Solution { public int titleToNumber(String s) { int result = 0; for (int i = 0; i < s.length(); i++) { result = result * 26 + (s.charAt(i) - 'A' + 1); } return result; } } }
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// OJ: https://leetcode.com/problems/excel-sheet-column-number/ // Time: O(N) // Space: O(1) class Solution { public: int titleToNumber(string s) { int ans = 0; for (char c : s) ans = ans * 26 + (c - 'A' + 1); return ans; } };
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class Solution(object): def titleToNumber(self, s): """ :type s: str :rtype: int """ letters = {"A": 1, "B": 2, "C": 3, "D": 4, "E": 5, "F": 6, "G": 7, "H": 8, "I": 9, "J": 10, "K": 11, "L": 12, "M": 13, "N": 14, "O": 15, "P": 16, "Q": 17, "R": 18, "S": 19, "T": 20, "U": 21, "V": 22, "W": 23, "X": 24, "Y": 25, "Z": 26} s = s.upper() ret = 0 b = 0 for c in reversed(s): ret += letters[c] * 26 ** (b) b += 1 return ret