171. Excel Sheet Column Number

Runtime    1 ms
Beats     99.40%


Memory    41.1 MB
Beats     68.75%


class Solution {
    public int titleToNumber(String s) {
        int i=s.length()-1;
        int k = 1;
        int ans = 0;
        while(i>=0)
        {
            ans += ((s.charAt(i)-'@')*k);
            k *= 26;
            i--;
        }
        return ans;
    }
}