leetcode Excel Sheet Column Number

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 

思路，就是26进制转化为10进制。

'A' 的Asci码是65，对应的十进制是1，所以delta为64

int char2number(char c){    int numofchar = (int)c;    const int delta = 64;    return numofchar-delta;}int titleToNumber(char* s) {    int sum=0;    int n = strlen(s)-1;    while(*s){        sum+=char2number(*s)*pow(26,n);        n--;        s++;    }        return sum;}