Given a positive integer, return its corresponding column title as appear in an Excel sheet.
For example:
1 -> A
2 -> B
3 -> C
...
26 -> Z
27 -> AA
28 -> AB
Credits:
Special thanks to @ifanchu for adding this problem and creating all test cases.
本质上就是将一个10进制数转换为一个26进制的数
注意:由于下标从1开始而不是从0开始,因此要减一操作。
The Best Answer:
/**
* 最好的方式
*/
public String convertToTitle2(int n) {
String ret = "";
while (n != 0) {
ret = (char) ((n - 1) % 26 + 'A') + ret;
n = (n - 1) / 26;
}
return ret;
}
再提供一种递归一种非递归的方式,都是Accept!
递归形式:
/**
* 递归形式
*
* @param n
* @return
*/
public String convertToTitle(int n) {
if (n == 0)
return "";
if (n <= 26)
return intToStr(n);
String str = "";
int temp = n % 26;
int i = n / 26;
if (temp == 0)
i--;
str += convertToTitle(i);
str += intToStr(temp);
return str;
}
public String intToStr2(int x) {
switch (x) {
case 0:
return "A";
case 1:
return "B";
case 2:
return "C";
case 3:
return "D";
case 4:
return "E";
case 5:
return "F";
case 6:
return "G";
case 7:
return "H";
case 8:
return "I";
case 9:
return "J";
case 10:
return "K";
case 11:
return "L";
case 12:
return "M";
case 13:
return "N";
case 14:
return "O";
case 15:
return "P";
case 16:
return "Q";
case 17:
return "R";
case 18:
return "S";
case 19:
return "T";
case 20:
return "U";
case 21:
return "V";
case 22:
return "W";
case 23:
return "X";
case 24:
return "Y";
case 25:
return "Z";
}
return "";
}
非递归形式:
/**
* 非递归形式
*
* @param n
* @return
*/
public String convertToTitle1(int n) {
if (n == 0)
return "";
if (n <= 26)
return intToStr(n);
String str = "";
int temp = 0;
while (n != 0) {
temp = (n - 1) % 26;
str = intToStr2(temp) + str;
n = (n - 1) / 26;
}
return str;
}
public String intToStr2(int x) {
switch (x) {
case 0:
return "A";
case 1:
return "B";
case 2:
return "C";
case 3:
return "D";
case 4:
return "E";
case 5:
return "F";
case 6:
return "G";
case 7:
return "H";
case 8:
return "I";
case 9:
return "J";
case 10:
return "K";
case 11:
return "L";
case 12:
return "M";
case 13:
return "N";
case 14:
return "O";
case 15:
return "P";
case 16:
return "Q";
case 17:
return "R";
case 18:
return "S";
case 19:
return "T";
case 20:
return "U";
case 21:
return "V";
case 22:
return "W";
case 23:
return "X";
case 24:
return "Y";
case 25:
return "Z";
}
return "";
}
自然没有第一种解决巧妙,直接用余数+’A’,这样就可以直接得出需要的结果字符,而不需要用数组或者这种长长的switch语句。