Word Pattern is a problem which is solved using Hashmap
Let’s take a look at some examples for better understanding of the question.
Example 1:
Input : pattern = “abba”, s = “dog cat cat dog”
Output : true
Explanation : ‘a’ is mapped with dog and ‘b’ is mapped with cat
Example 2:
Input: pattern = “abba”, s = “dog cat cat fish”
Output: false
Explanation : a -> dog
b -> cat
a -> fish (Since ‘a’ is already mapped with dog and it cannot be used to map again with some other string. Hence, the result false)
Example 3: (An important test case)
Input : pattern = “abba”, s = “dog dog dog dog”
Output : false
Explanation : a -> dog
b -> dog
(Since ‘a’ is mapped with dog and ‘b’ is also mapping the same string. Hence, the result false)
Code
public boolean wordPattern(String pattern, String s) {
String arr[] = s.split(” “);
int n = arr.length;
if(pattern.length()!=n)
return false;
Map<Character, String> map = new HashMap<>();
for(int i=0; i<n; i++){
char ch = pattern.charAt(i);
if(map.containsKey(ch) && !(map.get(ch).equals(arr[i])))
return false;
if(!map.containsKey(ch) && map.containsValue(arr[i]))
return false;
map.put(ch, arr[i]);
}
return true;
}
}
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