0071. Simplify Path
https://leetcode.com/problems/simplify-path
Description
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.
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.
Example 4:
**Input:** path = "/a/./b/../../c/"
**Output:** "/c"
Constraints:
1 <= path.length <= 3000
path
consists of English letters, digits, period'.'
, slash'/'
or'_'
.path
is a valid absolute Unix path.
ac
// understanding of "simplify path" is the key
class Solution {
public String simplifyPath(String path) {
String[] list = path.split("/");
Stack<String> stack = new Stack<String>();
for (int i = 0; i < list.length; i++) {
switch (list[i]) {
case "":
case ".":
continue;
case "..":
if (!stack.isEmpty()) stack.pop();
break;
default:
stack.push(list[i]);
}
}
String res = "";
while (!stack.isEmpty()) {
res = "/" + stack.pop() + res;
}
return res.equals("") ? "/" : res;
}
}
// split by / , get a list
// use a stack or two pointer simulating a stack
// “/b/c/” - directory 'b ’ - > directory 'c '
// "." - current directory
// "./" - current directory
// "../" - one directory up
// e.g
// "/" : root directory
// "b/c/../" : it will go from c to b
// "c/b/./" : it is still in directory b
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