# 609. Find Duplicate File in System

#### Medium

***

Given a list `paths` of directory info, including the directory path, and all the files with contents in this directory, return *all the duplicate files in the file system in terms of their paths*. You may return the answer in **any order**.

A group of duplicate files consists of at least two files that have the same content.

A single directory info string in the input list has the following format:

* `"root/d1/d2/.../dm f1.txt(f1_content) f2.txt(f2_content) ... fn.txt(fn_content)"`

It means there are `n` files `(f1.txt, f2.txt ... fn.txt)` with content `(f1_content, f2_content ... fn_content)` respectively in the directory "`root/d1/d2/.../dm"`. Note that `n >= 1` and `m >= 0`. If `m = 0`, it means the directory is just the root directory.

The output is a list of groups of duplicate file paths. For each group, it contains all the file paths of the files that have the same content. A file path is a string that has the following format:

* `"directory_path/file_name.txt"`

 

**Example 1:**

<pre><code>Input: paths = ["root/a 1.txt(abcd) 2.txt(efgh)","root/c 3.txt(abcd)","root/c/d 4.txt(efgh)","root 4.txt(efgh)"]
<strong>Output:
</strong> [["root/a/2.txt","root/c/d/4.txt","root/4.txt"],["root/a/1.txt","root/c/3.txt"]]
</code></pre>

**Example 2:**

<pre><code>Input: paths = ["root/a 1.txt(abcd) 2.txt(efgh)","root/c 3.txt(abcd)","root/c/d 4.txt(efgh)"]
<strong>Output:
</strong> [["root/a/2.txt","root/c/d/4.txt"],["root/a/1.txt","root/c/3.txt"]]
</code></pre>

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**Constraints:**

* `1 <= paths.length <= 2 * 104`
* `1 <= paths[i].length <= 3000`
* `1 <= sum(paths[i].length) <= 5 * 105`
* `paths[i]` consist of English letters, digits, `'/'`, `'.'`, `'('`, `')'`, and `' '`.
* You may assume no files or directories share the same name in the same directory.
* You may assume each given directory info represents a unique directory. A single blank space separates the directory path and file info.

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**Follow up:**

* Imagine you are given a real file system, how will you search files? DFS or BFS?
* If the file content is very large (GB level), how will you modify your solution?
* If you can only read the file by 1kb each time, how will you modify your solution?
* What is the time complexity of your modified solution? What is the most time-consuming part and memory-consuming part of it? How to optimize?
* How to make sure the duplicated files you find are not false positive?

```python
class Solution:
    def findDuplicate(self, paths):
        M = collections.defaultdict(list)
        for line in paths:
            data = line.split()
            root = data[0]
            for file in data[1:]:
                name, _, content = file.partition('(')
                M[content[:-1]].append(root + '/' + name)

        return [x for x in M.values() if len(x) > 1]
        
```