leetcode--Word Pattern

题目：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-emptyword 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.

题目分析：按ab的模板形式，检验字符串是否符合模板。

One：运用Map键值对的形式进行检验

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

Two：进一步简化，利用map的put方法的返回值。

public class Solution {    public boolean wordPattern(String pattern, String str) {        String[] words = str.split(" ");    if (words.length != pattern.length())        return false;    Map index = new HashMap();    for (Integer i=0; i<words.length; ++i)        if (index.put(pattern.charAt(i), i) != index.put(words[i], i))            return false;    return true;    }}