## 题目描述：

LeetCode 388. Longest Absolute File Path

Suppose we abstract our file system by a string in the following manner:

The string `"dir\n\tsubdir1\n\tsubdir2\n\t\tfile.ext"` represents:

```dir
subdir1
subdir2
file.ext
```

The directory `dir` contains an empty sub-directory `subdir1` and a sub-directory `subdir2` containing a file `file.ext`.

The string `"dir\n\tsubdir1\n\t\tfile1.ext\n\t\tsubsubdir1\n\tsubdir2\n\t\tsubsubdir2\n\t\t\tfile2.ext"` represents:

```dir
subdir1
file1.ext
subsubdir1
subdir2
subsubdir2
file2.ext
```

The directory `dir` contains two sub-directories `subdir1` and `subdir2`. `subdir1` contains a file `file1.ext` and an empty second-level sub-directory `subsubdir1`. `subdir2` contains a second-level sub-directory `subsubdir2` containing a file `file2.ext`.

We are interested in finding the longest (number of characters) absolute path to a file within our file system. For example, in the second example above, the longest absolute path is `"dir/subdir2/subsubdir2/file2.ext"`, and its length is `32` (not including the double quotes).

Given a string representing the file system in the above format, return the length of the longest absolute path to file in the abstracted file system. If there is no file in the system, return `0`.

Note:

• The name of a file contains at least a `.` and an extension.
• The name of a directory or sub-directory will not contain a `.`.

Time complexity required: `O(n)` where `n` is the size of the input string.

Notice that `a/aa/aaa/file1.txt` is not the longest file path, if there is another path `aaaaaaaaaaaaaaaaaaaaa/sth.png`.

## 题目大意：

```dir
subdir1
subdir2
file.ext```

```dir
subdir1
file1.ext
subsubdir1
subdir2
subsubdir2
file2.ext```

• 文件名中至少包含一个点和一个扩展名。
• 目录名中不包含点。

## Python代码：

``````class Solution(object):
def lengthLongestPath(self, input):
"""
:type input: str
:rtype: int
"""
ans = lengthSum = 0
stack = [(-1, 0)]
for p in input.split('\n'):
depth = p.count('\t')
name = p.replace('\t', '')
topDepth, topLength = stack[-1]
while depth <= topDepth:
stack.pop()
lengthSum -= topLength
topDepth, topLength = stack[-1]
length = len(name) + (depth > 0)
lengthSum += length
stack.append((depth, length))
if name.count('.'):
ans = max(ans, lengthSum)
return ans
``````

## Python代码：

``````class Solution(object):
def lengthLongestPath(self, input):
"""
:type input: str
:rtype: int
"""
maxlen = 0
pathlen = {0: 0}
for line in input.splitlines():
name = line.lstrip('\t')
depth = len(line) - len(name)
if '.' in name:
maxlen = max(maxlen, pathlen[depth] + len(name))
else:
pathlen[depth + 1] = pathlen[depth] + len(name) + 1
return maxlen
``````

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