Leetcode Word Pattern

Given a

pattern

and a string

str

, find if

str

follows the same pattern.

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:

Both

pattern

and

str

contains only lowercase alphabetical letters.

Both

pattern

and

str

do not have leading or trailing spaces.

Each word in

str

is separated by a single space.

Each letter in

pattern

must map to a word with length that is at least 1.

解题思路：

使用HashMap, pattern 里的character 对应str 里的word.

注意：pattern =

"abba"

, str =

"dog dog dog dog"

should return false.

即当map里不包含key 时，还要检查是否已包含Value, 如果已含，那么return false.

另外，分割space 使用str.split("\\s+")

Java code:

public boolean wordPattern(String pattern, String str) {
String[] splited = str.split("\\s+");
if(pattern.length() != splited.length) {
return false;
}
Map<Character, String> map = new HashMap<Character, String>();
for(int i = 0; i < pattern.length(); i++){
if(!map.containsKey(pattern.charAt(i))) {
if(map.containsValue(splited[i])){
return false;
}
map.put(pattern.charAt(i), splited[i]);
}else{
if(!map.get(pattern.charAt(i)).equals(splited[i])){
return false;
}
}
}
return true;
}