139. Word Break

Given a string s and a dictionary of words dict, determine if s can be segmented into a space-separated sequence of one or more dictionary words.

For example, given
s = "leetcode",
dict = ["leet", "code"].

Return true because "leetcode" can be segmented as "leet code".

解题思路为Dynamic Programming。

令can[i]=true表示s.substring(0,i) can be segmented。

can[i] = true if can[j] == true and s.substring(j,i) in wordDict for 0<=j<i

public class Solution {
    public boolean wordBreak(String s, Set<String> wordDict) {
        if(s == null || wordDict == null) return false;
        int len = s.length();
        boolean[] can = new boolean[len+1];
        can[0] = true;
        for(int i = 1; i <= len; i++) {
            for(int j = 0; j < i; j++) {
                if(can[j] == true && wordDict.contains(s.substring(j, i))) can[i] = true;
            }
        }
        return can[len];
    }
}