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ExcelSheetColumnNumber .java
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executable file
·50 lines (41 loc) · 1.08 KB
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'A' - 'A' = 0. 所以 char - 'A' + 1 = 题目里的对应数位。
26位运算和10位一样嘛，num += 每位的digit * Math.pow(26, 数位号)。
```
/*
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
*/
public class Solution {//ABC -> 'A', 'B', 'C'
public int titleToNumber(String s) {//S = AA
int rst = 0;
char[] arr = s.toCharArray();
for (int i = 0; i < arr.length; i++) {//i = 0,1,2 // (char c : arr)
rst = rst * 26 + arr[i] - 'A' + 1;//rst =1, 26 + 1 = 27,
}
return rst;
}
}
//3.4.2016 recap
//digit * pow(26, digit position)
public class Solution {
public int titleToNumber(String s) {
if (s == null || s.length() == 0) {
return 0;
}
int num = 0;
for (int i = s.length() - 1; i >= 0; i--) {
int digit = s.charAt(i) - 'A' + 1;
num += digit * Math.pow(26, s.length() - i - 1);
}
return num;
}
}
```