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 
...

Example 1:

Input: "A" Output: 1 Example 2:

Input: "AB" Output: 28 Example 3:

Input: "ZY" Output: 701

Solution:

Be careful about overflow

int titleToNumber(string s) {
    int ans = 0;
    for (int i=0; i < s.size(); i++) {
        int temp =  ans * 26;
        if (temp / 26 != ans) return INT_MAX;
        ans = temp + s[i]-'A'+1;
    }
    return ans;
}