LeetCode-140.单词拆分 II(相关话题:动态规划、回溯)

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;
    }
}

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转载自blog.csdn.net/weixin_38823568/article/details/87814938