[LeetCode]Word Pattern II

public class Solution {
public boolean wordPatternMatch(String pattern, String str) {
return helper(pattern, str, new HashMap<Character, String>(), new HashMap<String, Character>());
}
public boolean helper(String pattern, String str, HashMap<Character, String> map1, HashMap<String, Character> map2) {
if (pattern.length() == 0 && str.length() == 0) {
return true;
}
if (pattern.length() == 0 || str.length() == 0) {
return false;
}
char ch = pattern.charAt(0);
if (map1.containsKey(ch)) {
String tmp = map1.get(ch);
if (tmp.length() > str.length() || !tmp.equals(str.substring(0, tmp.length()))) {
return false;
} else {
return helper(pattern.substring(1), str.substring(tmp.length()), map1, map2);
}
} else {
for (int i = 1; i <= str.length(); i++) {
if (map2.containsKey(str.substring(0, i))) {
continue;
}
map1.put(ch, str.substring(0, i));
map2.put(str.substring(0, i), ch);
if (helper(pattern.substring(1), str.substring(i), map1, map2)) {
return true;
}
map1.remove(ch);
map2.remove(str.substring(0, i));
}
}
return false;
}
}