> For the complete documentation index, see [llms.txt](https://liuyang89116.gitbook.io/my-leetcode-book/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://liuyang89116.gitbook.io/my-leetcode-book/chapter_2_string/problem_165_compare_version_numbers.md).

# Problem 165: Compare Version Numbers

> <https://leetcode.com/problems/compare-version-numbers/>

## 思路

1. 把version string parse成两个`String[]`,然后比较对应的数组的值
2. 一个问题是：1.1 和 1.1.3.4 怎么比？

   我们可以首先把他们补齐，取两者长的为他们的长度

```java
public class Solution {
    public int compareVersion(String version1, String version2) {
        String[] arr1 = version1.split("\\.");
        String[] arr2 = version2.split("\\.");
        int length = arr1.length > arr2.length ? arr1.length : arr2.length;

        for (int i = 0; i < length; i++) {
            Integer v1 = i < arr1.length ? Integer.parseInt(arr1[i]) : 0;
            Integer v2 = i < arr2.length ? Integer.parseInt(arr2[i]) : 0;
            if (v1 > v2) {
                return 1;
            } else if (v1 < v2) {
                return -1;
            } else {
                continue;
            }
        }

        return 0;
    }
}
```

## 易错点

1. split字符串

   对于普通的字符，我们可以通过简单的`String[] arr = s.split(",");`来parse; 但是对于特殊字符 我们需要有特别的方法`String[] str1 = version1.split("\\.");`和"."一样的字符还有"|", `String[] str1 = version1.split("\\|");`

   > <http://javadevnotes.com/java-string-split-tutorial-and-examples>
2. String转数字

   ```java
   int a = Integer.parseInt(str);
   Double b = Double.parseDouble(str);
   ```