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:

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.

双向映射，键和值同时不存在才能插入，否则检查，键映射不等于值、值存在没有对应的键，都不是双向映射。

public static boolean wordPattern(String pattern, String str)
{
int patlen=pattern.length();
int strlen=str.length();
if(patlen==0||strlen==0)
return false;

String[] strs=str.split(" ");
if(patlen!=strs.length)
return false;

HashMap<Character, String> hashmap=new HashMap<>(strs.length);
for(int i=0;i<patlen;i++)
{
char c=pattern.charAt(i);
String s=strs[i];
if(!hashmap.containsKey(c)&&!hashmap.containsValue(s))
hashmap.put(c, s);
else {
if(!hashmap.containsKey(c)||hashmap.get(c).compareTo(s)!=0)
return false;
}
}

return true;
}