CareerCup

-Firstly we take a/b in a string called currentdirectory
-Then we split "c/../d/e/../f" with delimiter as "/"
-When there is a ".." then we take a substring of the currentdirectory
-If there is a character, then we will append "/" and the character

public class FindResultantDirectory {

	private static String findResultingDirectory(String currentDirectory,
			String sequenceOfOperations) {

		String splitDirectories[] = sequenceOfOperations.split("/");

		for (int i = 0; i < splitDirectories.length; i++) {
			if (splitDirectories[i].equals("..")) {
				currentDirectory = currentDirectory.substring(0,
						currentDirectory.length() - 2);
			} else {
				currentDirectory = currentDirectory + "/" + splitDirectories[i];
			}
		}

		return currentDirectory;
	}

	public static void main(String[] args) {
		System.out.println(findResultingDirectory("a/b", "c/../d/e/../f"));
	}
}

We can use a stack for this problem.
Step 1: If destination doesn't start with root, enter source directories to stack
Step 2: Split source and destination around match of regular expression "/" and put each of them in array.
Step 3: If a ".." pattern is found, pop the last added directory from array, otherwise push it to array.
Step 4: to get the end directory, look at the topmost element of the array

package career.cup.yelp;

import java.util.ArrayList;
import java.util.Stack;

public class getDirectory {
	
	public static void main(String args[]){
		
		getDirectiry("/logs", "test/nodes/../modules/logs");
		getDirectiry("/logs", "test/nodes/../modules/logs/..");
	}
	
	public static void getDirectiry(String src, String destination){
		
		Stack<String> directoryStack = new Stack<String>();
		
		String[] listDestination = destination.split("/");
		String[] listHost = src.split("/");
		
		if(!destination.startsWith("/")){
			for(String str : listHost){
				if(!(str.matches(".."))){
					directoryStack.push(str);
				}
				else if((str.matches(".."))){
					directoryStack.pop();
				}
			}
		}
		
		for(String str : listDestination){
			if(!(str.matches(".."))){
				directoryStack.push(str);
			}
			else if((str.matches(".."))){
				directoryStack.pop();
			}
		}
		
		System.out.println(directoryStack);
	}

}

You can implement it by using a stack. At any point, top of the stack will be the present working directory. Add or remove elements to/from the stack according to the directory changing operation being performed.

What if directory names are longer than one character? Using currDir = currDir.substring(0, currDir.length()-2) wouldn't be correct in that case. Instead, we could find the occurrence of the last slash by using currDir.lastIndexOf("/") and take the substring from 0 to this index.

import java.util.*;
public class cdImplementation
{
  public static void main(String args[])
  {
    //('a/b','c/../d/e/..f')
    String input[] = new String[]{"a/b","c/../d/e/../f"};
    Stack<String> stack = new Stack<String>();
    String str = "";
    for (String word : input)
      for (String i : word.split("/"))
      {
        if (!i.equals(".."))
          stack.push(i);
        else
          stack.pop();
      }
    while (!stack.isEmpty())
    {
      str = stack.pop() + "/" + str ;
    }
    System.out.println(str);
  }
}