String - 71. Simplify Path

71. Simplify Path

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.

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"

思路：
题目意思简化一个unix系统下的路径。.代表当前目录， ..代表上一级目录，做法就是用栈来做，先把字符串根据 /切割成字符串数组，然后遍历数组，如果当前字符串是 .，就不管，继续下一个，如果是 ..就把栈顶元素弹出，其他情况就入栈，最后在把栈中的元素用 /拼接在一起就可以。

代码：

go：

func simplifyPath(path string) string {
    if path == "" {
        return path
    }
  
    var stack []string
    pathArr := strings.Split(path, "/")
    for _, p := range pathArr {
        if p == "." || p == "" {
            continue
        } else if p == ".." {
          if len(stack) != 0 {
            stack = stack[:len(stack)-1]
          }
        } else {
            stack = append(stack, p)
        }
    }
  
    return "/" + strings.Join(stack, "/")
}