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.
class Solution(object):
def simplifyPath(self,path):
"""
:type path: str
:rtype: str
"""# define stack
stack=list()
# split string
path=[p for p in path.split(‘/‘) if p]
for p in path:
if p == ‘.‘:
continueelif p == ‘..‘:
if stack:
stack.pop()
else:
stack.append(p)
return‘/‘+‘/‘.join(stack)
Solu=Solution()
path="/a/./b/../../c/"print(Solu.simplifyPath(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.
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.
Runtime: 14 ms, faster than 74.20% of Java online submissions for Simplify Path. Memory Usage: 37.2 MB, less than 1.00% of Java online submissions for Simplify Path.
class Solution {
public String simplifyPath(String path) {
String[] strs = path.split("/");
Stack<String> stack = new Stack<String>();
for (int i = 0; i < strs.length; i++) {
if (strs[i].isEmpty() || strs[i].equals(".")) {
continue;
}
if (strs[i].equals("..")) {
if (!stack.isEmpty()) stack.pop();
} else {
stack.push("/" + strs[i]);
}
}
StringBuilder sb = new StringBuilder();
for (String s: new ArrayList<String>(stack)) {
sb.append(s);
}
return stack.isEmpty() ? "/" : sb.toString();
}
}
public class Solution {
public static String simplifyPath(String path) {
if (path == null || path.length() == 0) {
return "/";
}
String[] strs = path.split("/");
LinkedList<String> list = new LinkedList<String>();
for (String str : strs) {
if (str.length() == 0 || ".".equals(str)) {
continue;
}
if ("..".equals(str)) {
list.pollLast();
continue;
}
list.addLast(str);
}
String result = "";
while (list.size() > 0) {
result += "/" + list.pollFirst();
}
return result.length() > 0 ? result : "/";
}
}
LeetCode - Medium - 71. Simplify Path
Topic
String
Stack
Description
https://leetcode.com/problems/simplify-path/
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.
Analysis
略
Submission
import java.util.LinkedList;
public class SimplifyPath {
// 方法一：我写的
public String simplifyPath(String path) {
LinkedList<String> dirs = new LinkedList<>();
for (int p1 = 0, p2 = 1; p2 <= path.length(); p2++) {
if (p2 == path.length() || path.charAt(p2) == ''/'') {
String dir = path.substring(p1 + 1, p2);
p1 = p2;
if (dir.equals("") || dir.equals("."))
continue;
if (dir.equals("..")) {
if (!dirs.isEmpty())
dirs.removeLast();
} else {
dirs.add(dir);
}
}
}
StringBuilder sb = new StringBuilder();
dirs.stream().forEach(dir -> sb.append("/").append(dir));
return sb.length() == 0 ? "/" : sb.toString();
}
// 方法二：别人写的，写得更简洁
public String simplifyPath2(String path) {
LinkedList<String> list = new LinkedList<>();
for (String cur : path.split("/")) {
if (cur.equals("..")) {
if (!list.isEmpty())
list.removeLast();
} else if (cur.length() > 0 && !cur.equals("."))
list.add(cur);
}
return "/" + String.join("/", list);
}
}
Test
import static org.junit.Assert.*;
import org.junit.Test;
public class SimplifyPathTest {
@Test
public void test() {
SimplifyPath obj = new SimplifyPath();
assertEquals("/home", obj.simplifyPath("/home/"));
assertEquals("/", obj.simplifyPath("/../"));
assertEquals("/home/foo", obj.simplifyPath("/home//foo/"));
assertEquals("/c", obj.simplifyPath("/a/./b/../../c/"));
assertEquals("/home", obj.simplifyPath2("/home/"));
assertEquals("/", obj.simplifyPath2("/../"));
assertEquals("/home/foo", obj.simplifyPath2("/home//foo/"));
assertEquals("/c", obj.simplifyPath2("/a/./b/../../c/"));
}
}
![19.2.13 [LeetCode 71] Simplify Path](http://www.gvkun.com/zb_users/upload/2025/01/a934f267-7b16-4bb5-bc28-55e64e5d9adf1737594617725.jpg "19.2.13 [LeetCode 71] Simplify Path")
