【LeetCode】Word Pattern 解题报告

【LeetCode】Word Pattern 解题报告

标签（空格分隔）： LeetCode

题目地址：https://leetcode.com/problems/word-pattern/#/description

题目描述：

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:
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:

You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.

Ways

这个题第一感觉就是使用HashMap，看到Tags也是HashMap我就放心了。想法基本就是把字符和单词对应起来，看单词和字符能不能对应上，这样就知道模式是否匹配了。做的时候出现了一个小问题，就是

pattern = "abba", str = "dog dog dog dog"

这种，要判断是不是已经放进了value，之前不知道怎么办，今天学到了HashMap有个containsValue()方法，可以判断是否已经放进了value。

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

Date

2017 年 5 月 19 日