Reverse Integer

最新推荐文章于 2020-07-05 10:18:11 发布

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博客围绕LeetCode整数反转问题展开，给出示例，如123反转成321， -123反转成 -321。还提出编码前需考虑的问题，像整数末位为0时输出情况，以及反转后可能溢出的处理，最后提及解决方案。

问题描述

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?

Throw an exception? Good, but what if throwing an exception is not an option? You would then have to re-design the function (ie, add an extra parameter).

解决方案

public class Solution {
    public int reverse(int x) {
        String prefix = "";             // 用作保存前缀
	    if( x < 0 ) {
	        x = -x;
	        prefix = "-";
	    }
	    StringBuilder sb = new StringBuilder( prefix );
	    String reverse = new StringBuilder(String.valueOf(x)).reverse().toString();
	    String str = sb.append( reverse ).toString();

	    return Integer.parseInt( str );
    }
}