Find the Shortest Superstring

class Solution {
    String ans;


    public String shortestSuperstring(String[] words) {
        ans = "";

        fun(words, 0);

        // System.out.println(String.format(" %s ", merge2Strings("","baa")));
        // System.out.println(String.format(" %s ", merge2Strings("vv","")));
        return ans;
    }
    public void fun(String[] words, int idx){
        if(idx >= words.length){

            // for(String item : words){
            //     System.out.print(String.format(" %s", item));
            // }System.out.println();
            String possibleSolution = mergeOrderedList(words);
            // System.out.println(possibleSolution);
            if(ans == "" || ans.length() > possibleSolution.length()){
                ans = possibleSolution;
            }
            return;
        }
        for(int i=idx;i<words.length;++i){
            swap(words, idx, i);
            fun( words, idx+1);
            swap(words, idx, i);
        }
    }
    public void swap(String[] words, int a, int b ){
        String t = words[a];
        words[a] = words[b];
        words[b] = t;
    }
    public String mergeOrderedList(String[] words){
        if(words.length == 0) return "";
        if(words.length < 2) return words[0];
        String mergedString = words[0];
        for(int i=1;i<words.length;++i){
            mergedString = merge2Strings(mergedString, words[i]);
        }
        return mergedString;
    }
    public String merge2Strings(String a, String b){

        int lena = a.length();
        int lenb = b.length();
        int minLen = Math.min(lena, lenb);
        for(int k=minLen;k>=0;k--){
            boolean flag = true;
            for(int i=lena-k,j=0;i<lena;i++,j++){
                if(a.charAt(i) != b.charAt(j)){
                    flag = false; break;
                }
            }
            if(flag == true){
                return a.substring(0,lena-k)+b;
            }
        }
        return a+b;
    }
}

/*

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