leetcode上的pattern word问题

Posted 2020-06-08

问题：

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.

解释：本问题要求做到一一对应，所以可以想到Java中的Map集合

问题还是比较简单的，关键就是细节方面，要把所有的问题都要考虑进去

代码：

import java.util.*;

public class Solution {

    public boolean wordPattern(String pattern, String str) {

        Map map = new HashMap();

        char c;

        

        String[] a = str.split(" ");

        

        if(pattern.length() != a.length){

            return false;

        }

        

        map.put(pattern.charAt(0),a[0]);

        for(int i=1;i<a.length;i++){

            c=pattern.charAt(i);

            if(!map.containsKey(c) && !map.containsValue(a[i])){

                map.put(c,a[i]);

            }else if(!map.containsKey(c) && map.containsValue(a[i])){

                return false;

            }else{

                String s = (String)map.get(c);

                if(!s.equals(a[i])){

                    return false;

                }

            }

        }

        

        return true;

        

    }

}