LeetCode--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:

1. pattern = "abba", str = "dog cat cat dog" should return true.
2. pattern = "abba", str = "dog cat cat fish" should return false.
3. pattern = "aaaa", str = "dog cat cat dog" should return false.
4. 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.

大概题意： 1、对应的pattern - str是可以用hashmap组成的键值对；

               2、主要判断的是：map中是否存在key ：    

                                                 1、若不存在key，但存在value，则返回false；  

                                                 2、若存在key，  但是value与str的对应字符串不等，返回false；

                                      若都不存在，就添加新的 k-v对；

 

public class Solution {
     
    /**
     * 字符串模式匹配
     * @param pattern
     * @param str
     * @return
     */
   public boolean wordPattern(String pattern, String str) {
        if (pattern.isEmpty() || str.isEmpty())
            return false;
        String[] string = str.split(" ");
        if (pattern.length() != string.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(string[i]))
                    return false;
            } else if (hashMap.containsValue(string[i]))
                return false;
            else
                hashMap.put(pattern.charAt(i), string[i]);
        }
                return true;
    }
}

总结： 1、splith函数：在java.lang包中有String.split()方法,返回是一个数组    （http://www.cnblogs.com/liubiqu/archive/2008/08/14/1267867.html）   

         2、HashMap的各种操作：详见 http://tool.oschina.net/apidocs/apidoc?api=jdk_7u4

         3、字符串操作：              详见  http://tool.oschina.net/apidocs/apidoc?api=jdk_7u4