Leetcode 290 Word Pattern

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 word in str.

Examples:

1. pattern = "abba", str = "dog cat cat dog" should return true.
2. pattern = "abba", str = "dog cat cat fish" should return false.
3. pattern = "aaaa", str = "dog cat cat dog" should return false.
4. pattern = "abba", str = "dog dog dog dog" should return false.

Notes:
You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.

Solution 1: Use two hash map, compare last appearance of c and string.

 public class Solution {  
   public boolean wordPattern(String pattern, String str) {  
     int n=pattern.length();  
     String[] words=str.split(" ");  
     if (words.length!=n) return false;  
     Map<Character,Integer> mapChar=new HashMap<>();  
     Map<String,Integer> mapStr=new HashMap<>();  
     for (int i=0; i<n; i++) {  
       char c=pattern.charAt(i);  
       String s=words[i];  
       if (mapChar.containsKey(c)) {  
         if (mapStr.containsKey(s)) {  
           if (mapChar.get(c)>mapStr.get(s)) return false;  
           if (mapChar.get(c)<mapStr.get(s)) return false;  
         }  
         else return false;  
       }  
       else {  
         if (mapStr.containsKey(s)) return false;  
         else {  
           mapStr.put(s,i);  
           mapChar.put(c,i);  
         }  
       }  
     }  
     return true;  
   }  
 }