Simplify Path @LeetCode

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

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

click to show corner cases.

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".

	package leetcode;
	import java.util.ArrayList;
	/**
	* Solution: Split Path into word group. Consider "." ".." "" situation and construct absolute path.
	* Similar to Reverse words in a string
	*
	* "." current directory doesn't matter /a/./b == /a/b
	* ".." matters /a/../b == /b b is under /.
	* don't forget "". We should always consider this when we use split.
	*
	* Test Case: "/..." don't be confused! ... could be a directory!
	*
	* @author jeffwan
	* @date Apr 1, 2014
	*/
	public class SimplifyPath {
	public static String simplifyPath(String path) {
	String result = "/";
	String[] stubs = path.split("/");
	ArrayList<String> paths = new ArrayList<String>();
	for (String s : stubs) {
	if (s.equals("..")) {
	if (paths.size() > 0) {
	paths.remove(paths.size() - 1); // ".." go back parent directory. counteract last folder.
	}
	} else
	if (!s.equals(".") && !s.equals("")) {
	paths.add(s);
	}
	}
	//It's good to handle paths.size() == 0 situation, a "/" already be included in result.
	for (String s : paths) {
	result += s + "/";
	}
	if (result.length() > 1) {
	result = result.substring(0, result.length() - 1);
	}
	return result;
	}
	/*
	* My solution: scan from end to front. Intercept word and stores in list.
	* The result will be /word1/word2/word3. I ignore all "." because I think it's useless.
	* But I failed in such test case "/..." --> except "/..."
	* All in all, I didn't care the real relation between path and "." and ".."-- big mistake.
	*/
	public String simplifyPath2(String path) {
	if (path == null || path.length() == 0) {
	return "";
	}
	ArrayList<String> list = new ArrayList<String>();
	for (int i = path.length() - 1; i >= 0; i--) {
	if (path.charAt(i) == '/') {
	continue;
	}
	if (path.charAt(i) == '.') {
	break;
	}
	int end = i;
	while (path.charAt(i) != '/') {
	i--;
	}
	String word = path.substring(i + 1, end + 1);
	list.add(0, word);
	}
	if (list.size() == 0) {
	return "/";
	}
	StringBuilder sb = new StringBuilder();
	for (String word : list) {
	sb.append('/');
	sb.append(word);
	}
	return sb.toString().substring(0, sb.length());
	}
	}

view raw SimplifyPath.java hosted with ❤ by GitHub