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Simplify Path

题目

题目链接：

Given an absolute path for a file (Unix-style), simplify it. Or in other words, convert it to the canonical path.

In a UNIX-style file system, a period . refers to the current directory. Furthermore, a double period .. moves the directory up a level.

Note that the returned canonical path must always begin with a slash /, and there must be only a single slash / between two directory names. The last directory name (if it exists) must not end with a trailing /. Also, the canonical path must be the shortest string representing the absolute path.

Example 1:

Input: "/home/"Output: "/home"Explanation: Note that there is no trailing slash after the last directory name.

Example 2:

Input: "/../"Output: "/"Explanation: Going one level up from the root directory is a no-op, as the root level is the highest level you can go.

Example 3:

Input: "/home//foo/"Output: "/home/foo"Explanation: In the canonical path, multiple consecutive slashes are replaced by a single one.

Example 4:

Input: "/a/./b/../../c/"Output: "/c"

Example 5:

Input: "/a/../../b/../c//.//"Output: "/c"

Example 6:

Input: "/a//bc/d//././/.."Output: "/a/b/c"

分析

给出一个Linux/Unix风格的绝对路径，要简化该路径。即将其转化成为一个标准的路径。

我们知道，在Linux/Unix中，路径名是以/开头的。.表示当前目录，..表示上一层目录。/表示根目录，其上一层目录仍然为根目录/。不能以/结尾（根目录只有一个/）。 需要注意的是，连续出现n个/，实际上也仅仅代表一个/，例如/home///user其实就是/home/user。

因此，我们可以使用/分割当前字符串，然后遍历得到的字符串数组。

对于第i个字符串：

• 当该字符串是空串""或者是"."，路径不变。
• 当该字符串是".."时，表示上一层路径，此时删除结果字符串最后一个目录。如果结果字符串为""，则保持不变。
• 其他情况下，添加/和当前字符串的值到结果字符串中。

最后，当结果字符串的长度为0时，添加/，然后返回。不为0时直接返回。

代码如下

class Solution {
       public String simplifyPath(String path) {
           StringBuilder result = new StringBuilder();        String[] strings = path.split("/");                for (int i = 0; i < strings.length; i++) {
           	if (strings[i].equals("") || strings[i].equals(".")) {
           		continue;        	} else if (strings[i].equals("..")) {
           		int index = result.lastIndexOf("/");        		if (index >= 0) {
           			result.delete(index, result.length());        		}			} else {
   				result.append('/');				result.append(strings[i]);			}        }                if (result.length() == 0) {
           	result.append('/');        }                return result.toString();    }}

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