題目描述：給定非空字符串s和包含非空單詞列表的字典wordDict，確定是否可以將s分割為一個(gè)或多個(gè)字典中所包含的單詞序列（通過空格區(qū)分）。
說明：
1.詞典中的同一個(gè)詞可以在分割中重復(fù)使用多次

2. 你可以假設(shè)字典不包含重復(fù)的單詞
   Example1：

Input: s = "leetcode", wordDict = ["leet", "code"]
Output: true
Explanation: Return true because "leetcode" can be segmented as "leet code".

Example2：

Input: s = "applepenapple", wordDict = ["apple", "pen"]
Output: true
Explanation: Return true because "applepenapple" can be segmented as "apple pen apple".
             Note that you are allowed to reuse a dictionary word.

Example3：

Input: s = "catsandog", wordDict = ["cats", "dog", "sand", "and", "cat"]
Output: false

通過函數(shù)遞歸調(diào)用判斷是否包含：

class Solution {
    Set<String> set=new HashSet<>();
    public boolean wordBreak(String s, List<String> wordDict) {
        if(wordDict.contains(s))
            return true;
        if(set.contains(s))
            return false;
        for(String string:wordDict){
            if(s.startsWith(string)){
                if(wordBreak(s.substring(string.length()),wordDict))
                    return true;
            }
        }
        set.add(s);
        return false;
    }
}