leetcode 168 Excel表列名称 171 Excel 表列序号

class Solution {
public:
    string convertToTitle(int columnNumber) {
        int sum = columnNumber;
        long cols = 0;
        long tmp = 1;
        while(columnNumber){
            tmp = columnNumber;
            columnNumber/=26;
            if(tmp%26==0){
                --columnNumber;
            }
            ++cols;
        }
        std::cout<<"cols: "<<cols<<std::endl;

        std::string res="";
        int a = 0;
        for(int i=1;i<=cols;++i){
            sum-=pow(26,i-1);
        }
        //类比十进制 -> 特殊的26进制
        
        for(int i = cols;i>1;--i){
            a = pow(26,i-1);
            res+=(sum/a+'A');
            sum=sum%a;
        }
        res+=('A'+sum);
        
        return res;
    }
};

class Solution {
public:
    int titleToNumber(string columnTitle) {
        int res = 0;
        int a = 0;
        for(int i = columnTitle.size()-1;i>=1;--i){
            a=pow(26,i);
            res+=a;
        }

        for(int i = 0;i< columnTitle.size();++i){
            a = pow(26,columnTitle.size()-1-i);
            res += a*(columnTitle[i]-'A');
        }

        return res+1;
        
    }
};