LeetCode.158(171) Excel Sheet Column Title&Excel Sheet Column Number

题目158：

Given a positive integer, return its corresponding column title as appear in an Excel sheet.

For example:

1 -> A
2 -> B
3 -> C
...
26 -> Z
27 -> AA
28 -> AB

分析：

class Solution {
public String convertToTitle(int n) {
//给定整数，求其Excel表达
String res="";
while(n>0){
n--;
char c=(char)('A'+n%26);
res=String.valueOf(c)+res;
n/=26;
}
return res;
}
}

题目171:

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

class Solution {
public int titleToNumber(String s) {
//给定字符串，给出其整数表达
//类型于26进制(注意对应字母所在位置，需要加上其后面位数*25)
char [] ch=s.toCharArray();
int sum=0;
for(int i=0;i<ch.length;i++){
int temp=ch[i]-'A'+1;
sum+=temp*Math.pow(26,ch.length-1-i);
}
return sum;
}

}