LeetCode 171.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

class Solution {
public:
int titleToNumber(string s) {
long long number = 0;
for(int i = 0; i < s.length(); number *= 26,++i)
number += s[i] - 64;

number /= 26;

return number;
}
};

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