71. Simplify Path

Question

Given an absolute path for a file (Unix-style), simplify it.

For example,
path = "/home/", => "/home"
path = "/a/./b/../../c/", => "/c"
path = "/a/../../b/../c//.//", => "/c"
path = "/a//b////c/d//././/..", => "/a/b/c"

In a UNIX-style file system, a period ('.') refers to the current directory, so it can be ignored in a simplified path. Additionally, a double period ("..") moves up a directory, so it cancels out whatever the last directory was. For more information, look here: https://en.wikipedia.org/wiki/Path_(computing)#Unix_style

Corner Cases:

• Did you consider the case where path = “/../”?
• In this case, you should return “/”.
• Another corner case is the path might contain multiple slashes ‘/’ together, such as “/home//foo/”.
• In this case, you should ignore redundant slashes and return “/home/foo”.

Thinking（二刷）:

• Method 1: 实际上就是考察对栈进行运用，此时我们更倾向于使用LinkedList这种双向队列。

class Solution {
    public String simplifyPath(String path) {
        if(path == null || path.length() == 0) return "/";
        LinkedList<String> stack = new LinkedList<>();
        String[] tokens = path.split("/");
        for(String token : tokens){
            if(token.length() > 0){
                if(token.equals(".")) continue;
                else if(token.equals("..")){
                    if(!stack.isEmpty()) stack.pollLast();
                }else{
                    stack.add(token);
                }
            }
        }
        StringBuilder sb = new StringBuilder();
        if(stack.isEmpty()) return "/";
        while(!stack.isEmpty()){
            sb.append("/");
            sb.append(stack.pollFirst());
        }
        return sb.toString();
    }
}