leet-code/Java/71. Simplify Path.java at master · awangdev/leet-code · GitHub

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M
tags: String, Stack
time: O(n)
space: O(n)

给一个path, simplify成最简单形式. 注意考虑edgecase

#### Stack
- 理解unixpath:
 - 1. `.` 代表currentdirectory, 可以忽略.
 - 2. `../` 表示previouslevel.
 - 3.doubleslash可以忽略.
 - 4.emptystring要output `/`
- parseby'/', andgooverusingstack
 - put [folder] instack
 - ".."pop() 1elementofthestack, ifanything
 - "."staysthesame
- outputstackreversely: connectwith'/', skiptail

```
/*
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. For more information, see: Absolute path vs relative path in Linux/Unix

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//b////c/d//././/.."
Output: "/a/b/c"
*/
/*
- parse by '/', and go over using stack
 - put [folder] in stack
 - ".." pop() 1 element of the stack, if anything
 - "." stays the samee
- output stack reversely: connect with '/', skip tail /
*/

classSolution {
publicStringsimplifyPath(Stringpath) {
Stack<String> stack = newStack<>();
String[] parts = path.split("/");
for (Strings : parts) {
if (s.isEmpty() || s.equals(".")) continue;
if (s.equals("..")) {
if (!stack.isEmpty()) stack.pop();
continue;
 }
stack.push(s);
 }

// build output
StringBuffersb = newStringBuffer();
while (!stack.isEmpty()) sb.insert(0, "/" + stack.pop());
if (sb.length() == 0) sb.append("/");

returnsb.toString();
 }
}

```