LeetCode之Excel Sheet Column Number

1、题目

Related to question Excel Sheet Column Title

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 

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

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2、分析

A -> 1*26^0AA -> 1*26^1 + 1*26^0AAA -> 1*26^2 + 1*26^1 + 1*26^0

3、代码实现

public class Solution {    public int titleToNumber(String value) {       if (value == null || value.length() == 0) return 0;int length = value.length();//A 65char[] chars = value.toCharArray();int result = 0;int pow = 0;//please here is i >= 0 not is i > 0for (int i = length - 1; i >= 0; i--) {int tmp = chars[i] - 'A' + 1;int temp1 = (int)Math.pow(26, pow);pow++;result += tmp * temp1;}return result;     }}

4、总结

注意每次写

for(int i = length - 1; i > 0 --i)

的时候要注意不是这样写的，需要写成这样

for(int i = length - 1; i >= 0 --i)

不要忘记有=号，切记，以后不要换这样的错误。

还有求^的函数要知道，不要忘记

Math.pow(26, pow)