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*26^0
AA -> 1*26^1 + 1*26^0
AAA -> 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 65
char[] chars = value.toCharArray();
int result = 0;
int pow = 0;
//please here is i >= 0 not is i > 0
for (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)
