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. 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 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"
Example 5:
Input: "/a/../../b/../c//.//" Output: "/c"
Example 6:
Input: "/a//b////c/d//././/.." Output: "/a/b/c"
難度：medium
題目：給出unix風格的絕對路徑，簡化它。換名話說轉成canonical 路徑。 在unix風格系統裡。.指當前目錄。..指上一級目錄。
思路：stack
Runtime: 14 ms, faster than 74.20% of Java online submissions for Simplify Path.
Memory Usage: 37.2 MB, less than 1.00% of Java online submissions for Simplify Path.
class Solution {
public String simplifyPath(String path) {
String[] strs = path.split("/");
Stack<String> stack = new Stack<String>();
for (int i = 0; i < strs.length; i++) {
if (strs[i].isEmpty() || strs[i].equals(".")) {
continue;
}
if (strs[i].equals("..")) {
if (!stack.isEmpty()) stack.pop();
} else {
stack.push("/" + strs[i]);
}
}
StringBuilder sb = new StringBuilder();
for (String s: new ArrayList<String>(stack)) {
sb.append(s);
}
return stack.isEmpty() ? "/" : sb.toString();
}
}