OJ链接 ：139.单词拆分 

代码：

class Solution {public boolean wordBreak(String s, List<String> wordDict) {Set<String> set = new HashSet<String>(wordDict);int n = s.length();boolean[] dp = new boolean[n+1];dp[0] = true;//初始化 保证后边正常s = " " + s; //映射for(int i =1;i<=n; i++){for(int j =1;j<=i;j++){if( dp[j-1]==true && set.contains(s.substring(j,i+1))){dp[i]=true;break;}}}return dp[n];}
}