Solution.java

public class Solution {
    private class NodeFile {
        String name;
        List<NodeFile> list;
        int max=0;
        public NodeFile(String name) {
            this.name = name;
            this.list = new ArrayList<NodeFile>();
            this.max=name.contains(".")?name.length():0;
        }
    }

    public int lengthLongestPath(String input) {
        int max=0;
        String[] strs=input.split("\n");
        StringBuffer sb=new StringBuffer(strs[0]);
        for (int i = 1; i < strs.length; i++) {
            if (strs[i].substring(0,1).equals("\t")||(strs[i].length()>4&&strs[i].substring(0,4).equals("    "))) {
                sb.append('\n'+strs[i]);
            }else{
                NodeFile node=structureTreeFile(sb.toString());
                if (node.max>max) {
                    max=node.max;
                }
                sb=new StringBuffer(strs[i]);
            }
        }
        NodeFile node=structureTreeFile(sb.toString());
        if (node.max>max) {
            max=node.max;
        }
        return max;
    }

    public NodeFile structureTreeFile(String input) {
        if (input.length() > 0) {
            String[] strs = input.split("\n");
            StringBuffer sb = new StringBuffer();
            NodeFile ans = new NodeFile(strs[0]);
            int otherMax=0;
            for (int i = 1; i < strs.length; i++) {
                String s=strs[i];
                if (s.length()>4&&s.substring(0,4).equals("    ")) {
                    s=s.substring(4);
                }else{
                    s=s.substring(1);
                }
                if (s.contains("\t")) {
                    sb.append("\n"+s);
                } else {
                    NodeFile node = structureTreeFile(sb.toString());
                    if (node != null) {
                        ans.list.add(node);
                        if (node.max>otherMax) {
                            otherMax=node.max;
                        }
                    }
                    sb = new StringBuffer(s);
                }
            }
            NodeFile node = structureTreeFile(sb.toString());
            if (node != null) {
                ans.list.add(node);
                if (node.max>otherMax) {
                    otherMax=node.max;
                }
            }
            if (otherMax!=0) {
                ans.max=ans.name.length()+1+otherMax;
            }
            return ans;
        }
        return null;
    }
}