Easy-题目49：290. Word Pattern

题目原文：

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.

题目大意：

给出一个模式和字符串。判断字符串时候满足模式。这里模式和对应字符串要求是一一映射(bijection)的。（如果不知道啥叫一一映射，继续滚回去复习高中数学！）

题目分析：

这题和Easy第46题类似，使用两个HashMap维护双向的key-value对，一旦发现有重复的key返回false。

源码：（language：java）

public class Solution {
public boolean wordPattern(String pattern, String str) {
HashMap<Character,String> map=new HashMap();
HashMap<String,Character> map2=new HashMap();
String[] words=str.split(" ");
if(pattern.length()!=words.length)
return false;
for(int i=0;i<pattern.length();i++) {
Character key=pattern.charAt(i);
String word=words[i];
if(!map.containsKey(key))   {
if(!map2.containsKey(word))
{
map.put(key, word);
map2.put(word, key);
}
else
return false;
}
else if (!(map.get(key).equals(word) && map2.get(word).equals(key)))
return false;
}
return true;
}

}

成绩：

3ms，beats 18.29%，众数3ms，51.82%