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
类似26进制,当A出现在个位时代表1 出现在十位时代表26
class Solution {
public int titleToNumber(String s) {
int res = 0;
if(s==""||s==null)
return res;
for(int i =0;i<s.length();i++){
res = res*26 + s.charAt(i)-'A'+1;
}
return res;
}
}