71.Simplify Path
===

###### tags: `Medium`,`String`,`Stack`

[71. Simplify Path](https://leetcode.com/problems/simplify-path/)

### 題目描述

Given a string `path`, which is an **absolute path** (starting with a slash `'/'`) to a file or directory in a Unix-style file system, convert it to the simplified **canonical path**.

In a Unix-style file system, a period `'.'` refers to the current directory, a double period `'..'` refers to the directory up a level, and any multiple consecutive slashes (i.e. `'//'`) are treated as a single slash `'/'`. For this problem, any other format of periods such as `'...'` are treated as file/directory names.

The **canonical** path should have the following format:

* The path starts with a single slash `'/'`.
* Any two directories are separated by a single slash `'/'`.
* The path does not end with a trailing `'/'`.
* The path only contains the directories on the path from the root directory to the target file or directory (i.e., no period `'.'` or double period `'..'`)

Return *the simplified **canonical path**.*

### 範例

**Example 1:**

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

**Example 2:**

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

**Constraints**:

* 1 <= `path.length` <= 3000
* `path` consists of English letters, digits, period `'.'`, slash `'/'` or `'_'`.
* `path` is a valid absolute Unix path.

### 解答
#### Python

class Solution:
    def simplifyPath(self, path: str) -> str:
        stack = []
        path_list = path.split("/")

        for p in path_list:
            if not p or p == '.':
                continue
            elif p == '..':
                if stack:
                    stack.pop()
            else:
                stack.append(p)

        return "/" + "/".join(stack)

> [name=Ron Chen][time=Wed, Apr 12, 2023]

class Solution:
    def simplifyPath(self, path: str) -> str:
        path = path.split('/')
        s = []
        for p in path:
            if p == '':
                continue
            elif p == '.':
                continue
            elif p == '..':
                for i in range(min(len(s), 1)):
                    s.pop()
            else:
                s.append(p)

        return '/'+'/'.join(s)
            

#### Javascript

function simplifyPath(path) {
  const stack = [];
  const dirs = path.split('/');
  for (const dir of dirs) {
    if (dir === '..') {
      stack.pop();
    } else if (dir !== '.' && dir !== '') {
      stack.push(dir);
    }
  }

  return '/' + stack.join('/');
}

> [name=Marsgoat][time=Wed, Apr 12, 2023]

#### TypeScript

function simplifyPath(path: string): string {
  const stack: string[] = [];
  const pathArr = path.split('/');

  const emptyString = '';
  const onePeriod = '.';
  const doublePeriod = '..';

  pathArr.forEach((d) => {
    if (d === doublePeriod) {
      stack.pop();
    } else if (d !== onePeriod && d !== emptyString) {
      stack.push(d);
    }
  });

  return '/' + stack.join('/');
}

> [name=Sheep][time=Thu, Apr 13, 2023]

### Reference

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