LeetCode -- Excel Sheet Column Number

LeetCode -- Excel Sheet Column Number

題目描述：


Related to question Excel Sheet Column Title


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


本題可以轉化為進制轉換問題。


思路：和2進制轉10進制有點類似，對於AAA，可以理解為26進制的轉換：1*26 + 1*26^2 + 1*26^3




實現代碼：

public class Solution {
    public int TitleToNumber(string s) 
    {
    	var sum = 0;
    	for(var i = s.Length - 1; i >= 0; i--){
    		var d = s.Length - i;
    		var n = Num(s[i]);
    		sum += (int)Math.Pow(26, d-1) * n;
    	}
    	return sum;
    }
	
private int Num(char c)
{
	return (int)c - 64;
}


}