LeetCode:Word Pattern

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:

pattern =

"abba"

, str =

"dog cat cat dog"

should return true.

pattern =

"abba"

, str =

"dog cat cat fish"

should return false.

pattern =

"aaaa"

, str =

"dog cat cat dog"

should return false.

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 @minglotus6 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<Character, String> hashMap = new HashMap<Character, String>();
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;

}
}