Excel Sheet Column Number

package cn.edu.xidian.sselab;
/**
* title:Excel Sheet Column Number
* content:
* 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
*/
public class TitleToNumber {

//这是一个失败的案例，因为用了switch case的方式来求解，结果代码量非常大
//其实就是想知道A对应1，B对应2这样的结果，完全可以用得到的字符减去A加上1就可以得到值
public int titleToNumbers(String s){
int len = s.length();
int result = 0;
int position = 0;
for(int i=0;i<len;i++){
char temp = s.charAt(i);
position = position(temp);
result += Math.pow(26, len - i - 1) * position;
}
return result;
}
public int position(char temp){
int position = 0;
switch(temp){
case 'A': position = 1;break;
case 'B': position = 2;break;
case 'C': position = 3;break;
case 'D': position = 4;break;
case 'E': position = 5;break;
case 'F': position = 6;break;
case 'G': position = 7;break;
case 'H': position = 8;break;
case 'I': position = 9;break;
case 'J': position = 10;break;
case 'K': position = 11;break;
case 'L': position = 12;break;
case 'M': position = 13;break;
case 'N': position = 14;break;
case 'O': position = 15;break;
case 'P': position = 16;break;
case 'Q': position = 17;break;
case 'R': position = 18;break;
case 'S': position = 19;break;
case 'T': position = 20;break;
case 'U': position = 21;break;
case 'V': position = 22;break;
case 'W': position = 23;break;
case 'X': position = 24;break;
case 'Y': position = 25;break;
case 'Z': position = 26;break;
}
return position;
}

//正确的解法：
//这样就省去了上面麻烦的switch case来求解对应关系的代码，非常简洁了
//这其实就可以将题目转换成一个将字符转换成一个26进制的过程，注意不要算错就可以了
public int titleToNumber(String s){
int len = s.length();
int result = 0;
for(int i=0;i<len;i++){
char temp = s.charAt(i);
result += Math.pow(26, len - i - 1) * (temp - 'A' + 1);
}
return result;
}

}