private void getPair(String[] words, int idx, Map<String, Integer> strIdx, Set<List<Integer>> results) {
            String w = words[idx];
if (w.equals("aaa"))
	System.out.println();
            // with pivot
            for (int m = 0; m < w.length(); m++) {
                int l = m-1, r = m+1;
                while (l >= 0 && r < w.length()) {
                    if (w.charAt(l) != w.charAt(r))
                        break;
                    l--;
                    r++;
                }
                addResult(w, l, r, idx, strIdx, results);
            }
            // without pivot
            for (int m = 0; m <= w.length(); m++) {
                int r = m, l = r-1;
                while (l >= 0 && r < w.length()) {
                    if (w.charAt(l) != w.charAt(r))
                        break;
                    l--;
                    r++;
                }
                addResult(w, l, r, idx, strIdx, results);
            }
        }