LeetCode_171. Excel Sheet Column Number

171. Excel Sheet Column Number

Easy

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

package leetcode.easy;

public class ExcelSheetColumnNumber {
	@org.junit.Test
	public void test() {
		System.out.println(titleToNumber("A"));
		System.out.println(titleToNumber("AB"));
		System.out.println(titleToNumber("ZY"));
	}

	public int titleToNumber(String s) {
		int result = 0;
		int exponent = 0;
		for (int i = s.length() - 1; i >= 0; i--) {
			result += (s.charAt(i) - 'A' + 1) * Math.pow(26, exponent);
			exponent++;
		}
		return result;
	}
}