171. Excel Sheet Column Number

1. Question

Given a string columnTitle that represents the column title as appear in an Excel sheet, return its corresponding column number.

2. Examples

For example:

A -> 1
B -> 2
C -> 3
...
Z -> 26
AA -> 27
AB -> 28 
...

Example 1:

Input: columnTitle = "A"
Output: 1

Example 2:

Input: columnTitle = "AB"
Output: 28

Example 3:

Input: columnTitle = "ZY"
Output: 701

Example 4:

Input: columnTitle = "FXSHRXW"
Output: 2147483647

3. Constraints

1 <= columnTitle.length <= 7
columnTitle consists only of uppercase English letters.
columnTitle is in the range ["A", "FXSHRXW"].

4. References

• 来源：力扣（LeetCode） 链接：https://leetcode-cn.com/problems/excel-sheet-column-number 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

5. Solutions

class Solution {
    public int titleToNumber(String columnTitle) {
        int res = 0;
        for(int i = 0; i <  columnTitle.length(); i++){
            int tmp = columnTitle.charAt(i) - 'A' + 1;
            res = res * 26 + tmp;
        }
        return res;
    }
}