LeetCode 171. Excel Sheet Column Number

原题链接在这里：https://leetcode.com/problems/excel-sheet-column-number/

题目：

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

题解：

Keep accumlating.

Time O(n). n = s.length().

Space O(1).

AC Java:

 1 public class Solution {
 2     public int titleToNumber(String s) {
 3         if(s == null || s.length() == 0){
 4             throw new IllegalArgumentException("Invalid input string.");
 5         }
 6         int res = 0;
 7         for(int i = 0; i<s.length(); i++){
 8             res = res*26 + (int)(s.charAt(i)-'A') + 1;
 9         }
10         return res;
11     }
12 }

类似Excel Sheet Column Title. 

posted @ 2015-08-14 00:37  Dylan_Java_NYC  阅读(184)  评论(0)  编辑  收藏  举报