71.Simplify-Path

71. Simplify Path

题目地址

https://leetcode.com/problems/simplify-path/

题目描述

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"

代码

Approach #1 Using Stacks

class Solution {
  public String simplifyPath(String path) {
        if (path.isEmpty()) return path;

    Stack<String> stack = new Stack<String>();
    String[] components = path.split("/");

    for (String directory : components) {
      if (directory.equals(".") || directory.isEmpty()) {
        continue;
      } 
      else if (directory.equals("..")) {
        if (!stack.isEmpty()) {
          stack.pop();
        }
      } else {
        stack.add(directory);
      }
    }

    StringBuilder result = new StringBuilder();
    for (String dir : stack) {
      result.append("/");
      result.append(dir);
    }

    return result.length() > 0 ? result.toString() : "/";
  }
}