[LeetCode 290] Word Pattern

最新推荐文章于 2021-12-24 17:28:08 发布

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本文介绍了一种基于模式字符串和目标字符串的匹配算法实现。通过使用哈希表来映射模式字符到目标字符串中的单词，确保模式与字符串严格一致。文章详细解释了算法的工作原理，并提供了一个简洁的Java代码示例。

Given a pattern and a string str, find if str follows the same pattern.

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:

patterncontains only lowercase alphabetical letters, and str contains words separated by a single space. Each word in str contains only lowercase alphabetical letters.
Both pattern and str do not have leading or trailing spaces.
Each letter in pattern must map to a word with length that is at least 1.

solution:

straight forward, use hashtable to store current map from pattern character to str string. If there exits and not match or string maps more than one letter return false.

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))) {
                if(map.containsValue(strs[i])) return false;
                map.put(pattern.charAt(i), strs[i]);
            }else {
                if(strs[i].equals(map.get(pattern.charAt(i)))) continue;
                else return false;
            }
        }
        return true;
    }