71. Simplify Path

🟠   🔖  栈 字符串  🔗 LeetCode

题目

Given a string path, which is an absolute path (starting with a slash '/') to a file or directory in a Unix-style file system, convert it to the simplified canonical path.

In a Unix-style file system, a period '.' refers to the current directory, a double period '..' refers to the directory up a level, and any multiple consecutive slashes (i.e. '//') are treated as a single slash '/'. For this problem, any other format of periods such as '...' are treated as file/directory names.

The canonical path should have the following format:

• The path starts with a single slash '/'.
• Any two directories are separated by a single slash '/'.
• The path does not end with a trailing '/'.
• The path only contains the directories on the path from the root directory to the target file or directory (i.e., no period '.' or double period '..')

Return the simplified canonical path.

Example 1:

Input: path = "/home/"

Output: "/home"

Explanation: Note that there is no trailing slash after the last directory name.

Example 2:

Input: path = "/../"

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: path = "/home//foo/"

Output: "/home/foo"

Explanation: In the canonical path, multiple consecutive slashes are replaced by a single one.

Constraints:

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

题目大意

给你一个字符串 path ，表示指向某一文件或目录的 Unix 风格 绝对路径 （以 '/' 开头），请你将其转化为更加简洁的规范路径。

在 Unix 风格的文件系统中，一个点（.）表示当前目录本身；此外，两个点 （..） 表示将目录切换到上一级（指向父目录）；两者都可以是复杂相对路径的组成部分。任意多个连续的斜杠（即，'//'）都被视为单个斜杠 '/' 。 对于此问题，任何其他格式的点（例如，'...'）均被视为文件/目录名称。

请注意，返回的 规范路径 必须遵循下述格式：

• 始终以斜杠 '/' 开头。
• 两个目录名之间必须只有一个斜杠 '/' 。
• 最后一个目录名（如果存在）不能 以 '/' 结尾。
• 此外，路径仅包含从根目录到目标文件或目录的路径上的目录（即，不含 '.' 或 '..'）。

返回简化后得到的 规范路径 。

解题思路

这道题利用栈先进后出的特性处理上级目录 '..'，最后组装化简后的路径即可。

代码

/**
 * @param {string} path
 * @return {string}
 */
var simplifyPath = function (path) {
  const arr = path.split("/");
  let stack = [];
  for (let i of arr) {
    if (i == "" || i == ".") {
      continue;
    } else if (i == "..") {
      if (stack.length > 0) stack.pop();
    } else {
      stack.push(i);
    }
  }
  return "/" + stack.join("/");
};