给定一个非空字符串 s 和一个包含非空单词列表的字典 wordDict,在字符串中增加空格来构建一个句子,使得句子中所有的单词都在词典中。返回所有这些可能的句子。
说明:
- 分隔时可以重复使用字典中的单词。
- 你可以假设字典中没有重复的单词。
示例 1:
输入:
s = "catsanddog"
wordDict = ["cat", "cats", "and", "sand", "dog"]
输出:
[
"cats and dog",
"cat sand dog"
]
示例 2:
输入:
s = "pineapplepenapple"
wordDict = ["apple", "pen", "applepen", "pine", "pineapple"]
输出:
[
"pine apple pen apple",
"pineapple pen apple",
"pine applepen apple"
]
解释: 注意你可以重复使用字典中的单词。
示例 3:
输入:
s = "catsandog"
wordDict = ["cats", "dog", "sand", "and", "cat"]
输出:
[]
Java代码:
class Solution {
public List<String> wordBreak(String s, List<String> wordDict) {
return dfs(s, wordDict, new HashMap<>());
}
private List<String> dfs(String s, List<String> wordDict, HashMap<String, LinkedList<String>> map) {
if (map.containsKey(s))
return map.get(s);
LinkedList<String> res = new LinkedList<>();
if (s.isEmpty()) {
res.add("");
return res;
}
for (String word: wordDict) {
if (!s.startsWith(word))
continue;
List<String> tmp = dfs(s.substring(word.length()), wordDict, map);
for (String subStr: tmp)
res.add(word + (subStr.isEmpty() ? "" : " ") + subStr);
}
map.put(s, res);
return res;
}
}