Untitled

// User function Template for Java
import java.util.stream.Collectors;
class Solution {
    private boolean isValid(int idx, String str){
        return idx < str.length();
    }
    
    boolean isCyclic(int currNode, List<List<Integer>> adj, int[] nodeStates, List<Integer> ans){
        if(nodeStates[currNode] == 1 || nodeStates[currNode] == 2){
            return nodeStates[currNode] == 1;
        }
        nodeStates[currNode] = 1;
        for(int letter : adj.get(currNode)){
            if(isCyclic(letter, adj, nodeStates, ans)){
                return true;
            }
        }
        ans.add(currNode);
        nodeStates[currNode] = 2;
        return false;
    }
    
    public String findOrder(String[] words) {
        // code here
        List<List<Integer>> adj = new ArrayList<>();
        for(int i=0; i<26; i++){
            adj.add(new ArrayList<>());
        }
        if(words.length == 1){
        } else {
            for(int i=1; i<words.length; i++){
                int x = 0, y = 0;
                while(isValid(x, words[i-1]) && isValid(y, words[i]) && words[i-1].charAt(x) == words[i].charAt(y)){
                    ++x;
                    ++y;
                }
                if(x!=words[i-1].length() && y!=words[i].length()){
                    adj.get(words[i-1].charAt(x) - 'a').add(words[i].charAt(y) - 'a');
                } else if(x!=words[i-1].length() && y==words[i].length()){
                    // System.out.println("it breaks at i: " + i);
                    return "";
                }
            }
        }
        List<Integer> ans = new ArrayList<>();
        int[] nodeStates = new int[26];
        for(String word : words){
            for(int i=0; i<word.length(); i++){
                if(isCyclic(word.charAt(i) - 'a', adj, nodeStates, ans)){
                    return "";
                }
            }
        }
        Collections.reverse(ans);
        return ans.stream().map(diff -> String.valueOf((char) ('a' + diff))).collect(Collectors.joining());
    }
}