Java [leetcode 7] Reverse Integer

標籤：

問題描述：

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

Have you thought about this?

Here are some good questions to ask before coding. Bonus points for you if you have already thought through this!

If the integer‘s last digit is 0, what should the output be? ie, cases such as 10, 100.

Did you notice that the reversed integer might overflow? Assume the input is a 32-bit integer, then the reverse of 1000000003 overflows. How should you handle such cases?

For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

解題思路：

需要考慮數值為負的情況，需要考慮數值反過來後溢出的情況。

代碼如下：

 1 public class Solution { 2     public int reverse(int x) { 3         final String LowerValue = "2147483648"; 4         final String UpperValue = "2147483647"; 5         final int maxlength = 10; 6         String sOriginal = String.valueOf(x); 7         String sReverse = stringReverse(sOriginal); 8         String sfinal = new String(); 9         int reversenum;10         11         if (sReverse.charAt(sReverse.length() - 1) == ‘-‘) {12             sfinal = sReverse.substring(0, sReverse.length() - 1);13             if (sfinal.length() >= maxlength && sfinal.compareTo(LowerValue) > 0)14                 reversenum = 0;15             else16                 reversenum = -Integer.valueOf(sfinal).intValue();17         } else {18             sfinal = sReverse;19             if (sfinal.length() >= maxlength && sfinal.compareTo(UpperValue) > 0)20                 reversenum = 0;21             else22                 reversenum = Integer.valueOf(sfinal).intValue();23         }24         return reversenum;25     }26 27     public String stringReverse(String s) {28         StringBuilder stringBuilder = new StringBuilder(s);29         stringBuilder.reverse();30         return stringBuilder.toString();31     }32 }

 

Java [leetcode 7] Reverse Integer