LeetCode_71_Simplify Path (Java)

71. Simplify Path

Medium

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You are given an absolute path for a Unix-style file system, which always begins with a slash '/'. Your task is to transform this absolute path into its simplified canonical path.

The rules of a Unix-style file system are as follows:

• A single period '.' represents the current directory.
• A double period '..' represents the previous/parent directory.
• Multiple consecutive slashes such as '//' and '///' are treated as a single slash '/'.
• Any sequence of periods that does not match the rules above should be treated as a valid directory or file name. For example, '...' and '....' are valid directory or file names.

The simplified canonical path should follow these rules:

• The path must start with a single slash '/'.
• Directories within the path must be separated by exactly one slash '/'.
• The path must not end with a slash '/', unless it is the root directory.
• The path must not have any single or double periods ('.' and '..') used to denote current or parent directories.

Return the simplified canonical path.

 

Example 1:

Input: path = "/home/"

Output: "/home"

Explanation:

The trailing slash should be removed.

Example 2:

Input: path = "/home//foo/"

Output: "/home/foo"

Explanation:

Multiple consecutive slashes are replaced by a single one.

Example 3:

Input: path = "/home/user/Documents/../Pictures"

Output: "/home/user/Pictures"

Explanation:

A double period ".." refers to the directory up a level (the parent directory).

Example 4:

Input: path = "/../"

Output: "/"

Explanation:

Going one level up from the root directory is not possible.

Example 5:

Input: path = "/.../a/../b/c/../d/./"

Output: "/.../b/d"

Explanation:

"..." is a valid name for a directory in this problem.

 

Constraints:

• 1 <= path.length <= 3000
• path consists of English letters, digits, period '.', slash '/' or '_'.
• path is a valid absolute Unix path.

문제 풀이

/로 split 한 뒤 ..에 대한 경우의수를 나누었고 아무것도 없는 조건에서 바로 리턴하는 조건문도 추가했다.

코드

class Solution {
    public String simplifyPath(String path) {
        String[] dirArr = path.split("/");
        Deque<String> dq = new ArrayDeque<>();

        for(int i=0; i<dirArr.length; i++){
            if(!dirArr[i].equals(".") && !dirArr[i].isEmpty()){
                if(dirArr[i].equals("..")){
                    if(!dq.isEmpty()) dq.pollLast();
                }
                else{
                    dq.addLast(dirArr[i]);
                }
            }
        }
        StringBuilder sb = new StringBuilder();

        // case4 위한 조건문
        if(dq.isEmpty()) return "/";

        while(!dq.isEmpty()){
            sb.append("/").append(dq.poll());
        }
        return sb.toString();
    }
}