140. 单词拆分 II

字典树+dfs就完事了

class Solution {
public:
    int tree[10010][26];
    bool vis[10010];
    int cnt;
    vector<string> v;
    void build(string str)
    {
        int len = str.length();
        int rt = 0;
        for(int i = 0; i < len; i++)
        {
            int x = str[i] - 'a';
            if(tree[rt][x] == 0)
            {
                tree[rt][x] = ++cnt;
            }
            rt =  tree[rt][x];
        }
        vis[rt] = 1;
    }
    void dfs(string s, int k, string str)
    {
        if(k >= s.length())
        {
            v.push_back(str);
            return;
        }
        int rt = 0;
        int len = s.length();
        string tmp = "";
        while(k < len)
        {
            int x = s[k] - 'a';
            rt = tree[rt][x];
            if(rt == 0) break;
            tmp += s[k];
            if(vis[rt])
                dfs(s, k + 1, str == "" ? str + tmp : str + " " + tmp);
            k++;

        }
    }



    vector<string> wordBreak(string s, vector<string>& wordDict) {
        cnt = 0;
        memset(vis, 0, sizeof(vis));
        memset(tree, 0, sizeof(tree));
        int len = wordDict.size();
        for(int i = 0; i < len; i++)
        {
            build(wordDict[i]);
        }
        dfs(s, 0, "");
        return v;
 
    }
};