LeetCode - Simplify Path | Darren's Blog

Given an absolute path for a file (Unix-style), simplify it.
For example,
path = "/home/", => "/home"
path = "/a/./b/../../c/", => "/c"
The simplification of an absolute path can be done by first separating the path by "/" and interpreting each segment as subdirectory, current directory, or its parent directory. For ease of going back to the parent directory, we can use a stack to which a segment is pushed as long as it represents a subdirectory. Finally, the stack is converted into an array, and the simplified path is the concatenation of the segments in the stack preceded by a "/".

public String simplifyPath(String path) {

        if (path == null)

            return null;

        if (path.length() == 0)

            return "/";

        int n = path.length();

        Stack<String> stack = new Stack<String>();

        String[] directories = path.split("/");     // Separate path by "/"

        for (String dir : directories) {

            if (dir.length() != 0) {

                if (dir.equals("..")) {     // Go up to its parent

                    if (!stack.empty())

                        stack.pop();

                } else if (!dir.equals(".")) {  // Enter its subdirectory

                    stack.push(dir);

                }

            }

            // No redundant "/"

        }

        // Construct simplified path

        if (stack.empty())  // No subdirectory

            return "/";

        StringBuilder result = new StringBuilder();

        for (String s : stack.toArray(new String[stack.size()]))

            result.append("/"+s);

        return result.toString();

    }

}

Also refer to http://mounttop.blogspot.com/2014/03/leetcode-simplify-path.html
http://stupidcodergoodluck.wordpress.com/2013/11/16/leetcode-simplify-path/
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