Excel sheet column number

gistfile1.cpp

https://leetcode.com/problems/excel-sheet-column-number/

//Key point: this problem is just 26th-decimal transformation.

//input : only capital? no exception?
//O(l); l is the length of the given input

//test case
//A, Z, AA, BB, AAA

// trial: one time accepted!

class Solution {
public:
    int titleToNumber(string s) {
        map<char, int> dic;
        int res = 0;
        
        dic.insert(std::pair<char,int>('A',1));
        dic.insert(std::pair<char,int>('B',2));
        dic.insert(std::pair<char,int>('C',3));
        dic.insert(std::pair<char,int>('D',4));
        dic.insert(std::pair<char,int>('E',5));
        dic.insert(std::pair<char,int>('F',6));
        dic.insert(std::pair<char,int>('G',7));
        dic.insert(std::pair<char,int>('H',8));
        dic.insert(std::pair<char,int>('I',9));
        dic.insert(std::pair<char,int>('J',10));
        dic.insert(std::pair<char,int>('K',11));
        dic.insert(std::pair<char,int>('L',12));
        dic.insert(std::pair<char,int>('M',13));
        dic.insert(std::pair<char,int>('N',14));
        dic.insert(std::pair<char,int>('O',15));
        dic.insert(std::pair<char,int>('P',16));
        dic.insert(std::pair<char,int>('Q',17));
        dic.insert(std::pair<char,int>('R',18));
        dic.insert(std::pair<char,int>('S',19));
        dic.insert(std::pair<char,int>('T',20));
        dic.insert(std::pair<char,int>('U',21));
        dic.insert(std::pair<char,int>('V',22));
        dic.insert(std::pair<char,int>('W',23));
        dic.insert(std::pair<char,int>('X',24));
        dic.insert(std::pair<char,int>('Y',25));
        dic.insert(std::pair<char,int>('Z',26));
                                 
        for(int i=0; i<s.length(); ++i) {
            res += (int)pow(26.0, (s.length()-1-i))*dic[s[i]];
        }
     
        return res;
    }
};