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：
Input: "/home/"
Output: "/home"
Explanation: Note that there is no trailing slash after the last directory name.
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.
Input: "/home//foo/"
Output: "/home/foo"
Explanation: In the canonical path, multiple consecutive slashes are replaced by a single one.
Input: "/a/./b/../../c/"
Output: "/c"
Input: "/a/../../b/../c//.//"
Output: "/c"
Input: "/a//b////c/d//././/.."
Output: "/a/b/c"
解释下题目：
给定一个决定路径，将其简化
1. 利用堆栈
实际耗时：15ms
public String simplifyPath(String path) {
Deque<String> stack = new LinkedList<>();
Set<String> skip = new HashSet<>(Arrays.asList("..", ".", ""));
for (String dir : path.split("/")) {
//利用 "/"作为分隔符来分割
if (dir.equals("..") && !stack.isEmpty()) {
//如果是退回到上一级且栈中有东西，那么弹出
stack.pop();
} else if (!skip.contains(dir)) {
//判断下，如果不是本层或者没内容，那么就加入
stack.push(dir);
}
}
StringBuilder sb = new StringBuilder();
for (String dir : stack) {
//还原操作
sb.insert(0, dir);
sb.insert(0, "/");
}
return sb.toString().isEmpty() ? "/" : sb.toString();
}
踩过的坑：一开始还原的时候弄反了
思路很简单，就是利用堆栈来进行处理。
