leetcode [139]Word Break

Given a non-empty string s and a dictionary wordDict containing a list of non-emptywords, determine if s can be segmented into a space-separated sequence of one or more dictionary words.

Note:

• The same word in the dictionary may be reused multiple times in the segmentation.
• You may assume the dictionary does not contain duplicate words.

Example 1:

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

Example 2:

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.

Example 3:

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

题目大意：

查找一个词是否能被词典中的词构成，词典中的词并不重复。

解法：

使用动态规划求解，dp[i]代表着这个词前i个构成的词是否能被词典中的词组成。

java:

class Solution {
    public boolean wordBreak(String s, List<String> wordDict) {
        boolean []dp=new boolean[s.length()+1];
        dp[0]=true;
        for(int i=1;i<=s.length();i++){
            for(int j=0;j<i;j++){
                if(dp[j]&&wordDict.contains(s.substring(j,i))) {
                    dp[i]=true;break;
                }
            }
        }
        return dp[s.length()];
    }
}