[LeetCode]:171:Excel Sheet Column Number

题目：

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 

分析：

核心就是26进制转10进制，从低到高按位计算

代码：

public class Solution {
    public static int titleToNumber(String s) {
        int intResult = 0;
        char[]chars=s.toCharArray();
        int n =0;
        for(int i = chars.length; i>0;i--){
            intResult = intResult + ((int)chars[i-1]-64)*caleOffset(n);
            n++;
        }
        return intResult;
    }
   
    public static int caleOffset(int n) {
        int intResult = 1;
        for(int i = 0; i< n;i++){
            intResult = intResult*26;
        }
        return intResult;
    }
}

高手的代码：从高位到低位，进位乘以26

class Solution {
public:
    int titleToNumber(string s) {
        int ret = 0;
        for(int i = 0; i < s.size(); i ++)
            ret = ret*26 + (s[i]-'A'+1);
        return ret;
    }
};