[leetcode]71. Simplify Path简化路径

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 shorteststring 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"

题意

遇到"."的情况直接去掉，遇到".."删掉它上面挨着的一个路径， 求简化后的路径

思路

很接近real industry的题目

将input通过/分离出来， 利用Stack来模拟遇到"."和".."的情况

 

代码

class Solution {
    public String simplifyPath(String path) {
        String[] arr = path.split("/");
        StringBuilder sb = new StringBuilder();
        Stack<String> stack = new Stack<>();
        
        for (int i = 0; i<arr.length; i++) {
            if (arr[i].equals("..")) {
                if (!stack.isEmpty()) stack.pop();
            } else if (arr[i].equals(".")) {
                continue;                
            } else if (!arr[i].isEmpty()) {
                stack.push(arr[i]);
            }
        }
        
        if (stack.isEmpty()) return "/";
        
        // stack -> result String 
        while (!stack.isEmpty()) {
            sb.insert(0,  "/" + stack.pop());
        }     
        return sb.toString();      
    }
}