# 71. Simplify Path
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"
# Solution
Approach 1: Two pointers.
# Code (Python)
Approach 1:
# Code (C++)
Approach 1:
class Solution {
public:
string simplifyPath(string path) {
stack<string> dirs;
int head = 0;
int tail = 0;
while (tail <= path.size())
{
if (tail == path.size() || path[tail] == '/') // "tail == path.size()".
{
if (tail > head)
{
string dir = path.substr(head, tail - head);
if (dir != ".." && dir != ".")
dirs.push(dir);
else if (dir == ".." && !dirs.empty())
dirs.pop();
}
head = tail + 1;
}
tail++;
}
if (dirs.empty())
return "/";
string simplifiedPath;
while (!dirs.empty())
{
simplifiedPath = "/" + dirs.top() + simplifiedPath;
dirs.pop();
}
return simplifiedPath;
}
};