(String). 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

public class Solution {       //if不用hashmap，更好的方法是设置头尾“指针”，保证一个指向当前的值
public boolean wordPattern(String pattern, String str) {
String[] strs = str.split(" ");
if (pattern.length() != strs.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))
&& !(map.get(pattern.charAt(i))).equals(strs[i]))
return false;
if (!map.containsKey(pattern.charAt(i))
&& map.containsValue(strs[i]))
return false;
if (!map.containsKey(pattern.charAt(i))
&& !map.containsValue(strs[i]))
map.put(pattern.charAt(i), strs[i]);
}
return true;
}
}