【leetcode】Excel Sheet Column Title & Excel Sheet Column Number

public class Solution {
public String convertToTitle(int n) {
StringBuilder sb = new StringBuilder();
while (n > 0) {
int apd = n % 26;
char c;
if (apd == 0) {
c = 'Z';
n = n / 26 - 1;
} else
{
c = (char) (apd + 'A' - 1);
n = n / 26;
}
sb.append(c);
}
return sb.reverse().toString();
}
}

public class Solution {
public int titleToNumber(String s) {
HashMap<Character, Integer> map = new HashMap<Character, Integer>();
char c = 'A';
for(int i=1;i<=26;++i){
map.put(c,i);
c += 1;
}
int result = 0;
int i = s.length()-1;
int t = 0;
while(i >= 0){
char curr = s.charAt(i);
result = result + (int) Math.pow(26, t) * map.get(curr);
t++;
i--;
}
return result;
}
}

Math.pow(底数,几次方)
如：double a=2.0;
double b=3.0;
double c=Math.pow(a,b);
就是2的三次方是多少；
c最终为8；