【LeetCode】291.Word Pattern II(Hard)解题报告

【LeetCode】291.Word Pattern II(Hard)解题报告

题目地址：https://leetcode.com/problems/word-pattern-ii/

题目描述：

  Given a pattern and a string str, find if str follows the same pattern.

  Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty substring in str.

  Examples:

    pattern = “abab”, str = “redblueredblue” should return true.

    pattern = “aaaa”, str = “asdasdasdasd” should return true.

    pattern = “aabb”, str = “xyzabcxzyabc” should return false.

  Notes: You may assume both pattern and str contains only lowercase letters.

Solution:

//Edward shi
//实现题，就是backtracking，没有什么特别的技巧
public boolean wordPatterMatch(String pattern,String str){
HashMap<Character,String> map = new HashMap<>();
HashSet<String> set = new HashSet<>();
return isMatch(str,0,pattern,0,map,set);
}
private boolean isMatch(String str,int i,String pattern,int j,HashMap<Character,String> map,HashSet<String> set){
if(str.length() == i && j == pattern.length()) return true;
if(str.length() == i || j == pattern.length()) return false;

char c = pattern.charAt(j);
if(map.containsKey(c)){
String s = map.get(C);
if(!str.startsWith(s,j)){
return false;
}
return isMatch(str,i+s.length(),pattern,j+1,map,set);
}
for(int k=i ; k<str.length();k++){
String p = str.substring(i,k+1);
if(set.contains(p)){
continue;
}
map.put(c,p);
set.add(p);
if(isMatch(str,k+1,pattern,j+1,map,set)){
return true;
}
map.remove(c);
set.remove(p);
}
}

Date：2018年1月30日