171.excel-sheet-column-number.java

/*
 * @lc app=leetcode id=171 lang=java
 *
 * [171] Excel Sheet Column Number
 *
 * https://leetcode.com/problems/excel-sheet-column-number/description/
 *
 * algorithms
 * Easy (52.16%)
 * Likes:    612
 * Dislikes: 117
 * Total Accepted:    236K
 * Total Submissions: 452K
 * Testcase Example:  '"A"'
 *
 * 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
 *
 */
class Solution {
  public int titleToNumber(String s) {
    int factor = 1;
    int number = 0;
    for (int i = s.length() - 1; i >= 0; i--) {
      number += factor * (s.charAt(i) - 'A' + 1);
      factor *= 26;
    }
    return number;
  }
}