71. Simplify Path

Simplify Path

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".

Solution

public class Solution {
    public String simplifyPath(String path) {


          int prev = -1;

        List<String> components = new ArrayList<>();
        for (int i = 0; i < path.length(); i++) {
            if (path.charAt(i) == '/') {
                if (prev >= 0) {
                    components.add(path.substring(prev + 1, i));
                }

                prev = i;
            }
        }

          if (prev >= 0) {
            components.add(path.substring(prev+1));
        }


        List<String> filter = new ArrayList<>();
        for (String item : components) {
            if (item.equals(".")) {
                continue;
            }

            if (item.equals("..")) {
                if (!filter.isEmpty()) {
                    filter.remove(filter.size() - 1);
                }
            } else if (item.length() > 0){
                filter.add(item);
            }
        }

        StringBuffer sb = new StringBuffer();
        for(String item:filter) {
            sb.append("/");
            sb.append(item);
        }

        if (sb.length() == 0) {
            return "/";
        }

        return sb.toString();
    }
}