leetcode 290 word Pattern
z
 2018-03-03 22:57:22  

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.

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class Solution {
    public boolean wordPattern(String pattern, String str) {
        String[] words = str.split(" ");
        if(pattern.length() != words.length )
            return false;
        int n = pattern.length();
        HashMap<Character, String> m = new HashMap<Character, String>();
        for(int i=0; i<n; i++){
            if(m.containsKey(pattern.charAt(i))){
                if(!m.get(pattern.charAt(i)).equals(words[i])){
                    return false;
                }
            }
            else {
                if(m.containsValue(words[i]))
                    return false;
                m.put(pattern.charAt(i), words[i]);
            }
        }
        return true;
    }
}
  • 使用一个hashmap，值得注意的是题中的要求是一对一，不能一对对，也不能多对一。