longest repeated substring using simplest suffix tree

public class SuffixTree {

STNode root;

class STNode {

int data ;

STNode[] edges;

STNode(int d){

data = d;

}

STNode(){

}

}

//assume small cases: a-z

STNode addString(String s, int data){

if(root==null)

root = new STNode(-1);

STNode current = root;

int index = 0;

while(index<s.length()){

if(current.edges==null)

current.edges = new STNode[26];

int pos = s.charAt(index) - 'a';

if(current.edges[pos]==null)

current.edges[pos] = new STNode();

current = current.edges[pos];

index++;

}

current.data = data; //leaf store the position

return root;

}

public void addAllSubString(String s){

for(int i=0;i<s.length();i++){

this.addString(s.substring(i), i);

}

}

public String findLongestRepeatSub(String s){

this.addAllSubString(s);

Deque<STNode> sk = new ArrayDeque<STNode>();

sk.add(root);

int maxL = 0;

int currentL = 0;

STNode target = root;

while(!sk.isEmpty()){

Deque<STNode> temp = new ArrayDeque<STNode>();

while(!sk.isEmpty()){

STNode n = sk.remove();

currentL++;

int counter=0;

if(n.edges!=null){

for(STNode nd : n.edges){

if(nd!=null){

sk.add(nd);

counter++;

}

}

}

if(counter>1 || counter==1 && n.data>0){

if(currentL>maxL){

maxL = currentL;

target = n;

}

}

}

sk = temp;

}

int cn = 0;

//go down to the leaf if not on leaf yet.

while(target.data<=0){

if(target.edges!=null){

for(STNode nd : target.edges){

if(nd!=null){

target = nd;

cn++;

}

}

}

}

if(cn!=0)

return s.substring(target.data, s.length()-cn+1);

else

return s.substring(target.data, s.length());

}

}