problem:

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.

Credits:

Special thanks to  for adding this problem and creating all test cases.

 

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Solution:

 

public class Solution {    public boolean wordPattern(String pattern, String str) {        if (pattern.isEmpty() || str.isEmpty()) {            return false;        }                 String[] s = str.split(" ");        if (s.length != pattern.length()) {            return false;        }                 HashMap
     
       hashMap = new HashMap
      
       ();        for (int i = 0; i < pattern.length(); i++) {            if (hashMap.containsKey(pattern.charAt(i))) {                if (!hashMap.get(pattern.charAt(i)).equals(s[i])) {                    return false;                }            } else if (hashMap.containsValue(s[i])) {                return false;            } else {                hashMap.put(pattern.charAt(i), s[i]);            }        }                 return true;            }}