/**
Given a string s and a dictionary of strings wordDict, add spaces in s to
construct a sentence where each word is a valid dictionary word. Return all such
possible sentences in any order.
Note that the same word in the dictionary may be reused multiple times in the
segmentation.
Example 1:
Input: s = "catsanddog", wordDict = ["cat","cats","and","sand","dog"]
Output: ["cats and dog","cat sand dog"]
Example 2:
Input: s = "pineapplepenapple", wordDict = ["apple","pen","applepen","pine",
"pineapple"]
Output: ["pine apple pen apple","pineapple pen apple","pine applepen apple"]
Explanation: Note that you are allowed to reuse a dictionary word.
Example 3:
Input: s = "catsandog", wordDict = ["cats","dog","sand","and","cat"]
Output: []
Constraints:
1 <= s.length <= 20
1 <= wordDict.length <= 1000
1 <= wordDict[i].length <= 10
s and wordDict[i] consist of only lowercase English letters.
All the strings of wordDict are unique.
Related Topics字典树 | 记忆化搜索 | 哈希表 | 字符串 | 动态规划 | 回溯
👍 650, 👎 0
*/
//leetcode submit region begin(Prohibit modification and deletion)
class Solution {
public List<String> wordBreak(String s, List<String> wordDict) {
if (s == null || s.length() == 0 || wordDict == null || wordDict.size() == 0) {
return new ArrayList<>();
}
Map<Integer, List<String>> resultMap = new HashMap<>();
return wordBreakInner(s, s.length() - 1, resultMap, wordDict);
}
private List<String> wordBreakInner(String s, int index, Map<Integer, List<String>> resultMap, List<String> wordDict) {
if (resultMap.containsKey(index)) {
return resultMap.get(index);
}
List<String> result = new ArrayList<>();
for (String dict : wordDict) {
if (index + 1 < dict.length()) {
continue;
}
if (dict.equals(s.substring(index - dict.length() + 1, index + 1))) {
if (index + 1 == dict.length()) {
result.add(dict);
} else {
List<String> subResult = wordBreakInner(s, index - dict.length(), resultMap, wordDict);
if (subResult.size() > 0) {
for (String sub : subResult) {
result.add(sub + " " + dict);
}
}
}
}
}
resultMap.put(index, result);
return result;
}
}
//leetcode submit region end(Prohibit modification and deletion)
