Word Pattern
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.
分析
本题跟 "Isomorphic Strings" 很类似,用两个HashMap, 记录从字符到字符串和字符串到字符的映射。
代码
// Word Pattern
// Time Complexity: O(n), Space Complexity: O(n)
public class Solution {
public boolean wordPattern(String pattern, String str) {
String[] words = str.split(" ");
if (words.length != pattern.length()) return false;
final Map<Character, String> map1 = new HashMap<>();
final Map<String, Character> map2 = new HashMap<>();
for (int i = 0; i < words.length; ++i) {
final Character key1 = pattern.charAt(i);
if (map1.containsKey(key1)) {
final String value = map1.get(key1);
if (!value.equals(words[i])) return false;
} else {
map1.put(key1, words[i]);
}
final String key2 = words[i];
if (map2.containsKey(key2)) {
final char value = map2.get(key2);
if (value != pattern.charAt(i)) return false;
} else {
map2.put(key2, pattern.charAt(i));
}
}
return true;
}
}