Solution1239.java

import java.util.ArrayList;
import java.util.List;

/**
 * Created by slade on 2019/12/26.
 */
public class Solution1239 {
 public int maxLength(List<String> arr) {
 return dfs(0, "", arr);
 }

 public int dfs(int idx, String tmp, List<String> arr) {
 if (idx >= arr.size()) {
 return tmp.length();
 }

 String s = arr.get(idx);

 if (isNotDuplicate(s) && !isCross(tmp, s)) {
 return Math.max(dfs(idx + 1, tmp + s, arr), dfs(idx + 1, tmp, arr));
 } else {
 return dfs(idx + 1, tmp, arr);
 }
 }

 public Boolean isNotDuplicate(String s) {
 for (int i = 0; i < s.length(); i++) {
 char charWord = s.charAt(i);
 int fristPosition = s.indexOf(charWord);
 int lastPosition = s.lastIndexOf(charWord);
 if (fristPosition != lastPosition) {
 return false;
 }
 }
 return true;
 }

 public Boolean isCross(String s1, String s2) {
 for (int i = 0; i < s1.length(); i++) {
 for (int j = 0; j < s2.length(); j++) {
 if (s1.charAt(i) == s2.charAt(j)) {
 return true;
 }
 }
 }
 return false;
 }


 public static void main(String[] args) {
 Solution1239 solution1239 = new Solution1239();
 ArrayList arrayList = new ArrayList();
 arrayList.add("abcdefghijklmnopqrstuvwxyz");

 System.out.println(solution1239.maxLength(arrayList));
 }
}