G面经Prepare: Search word delete sequence in dictionary

给一个单词一个字典，每次删除单词里任一个字母直到剩下一个字母，形成一个序列，比如office->offce->ofce->ofc->oc->c。问是否字典里存在一个这种序列

 

package checkDictExistSequence;
import java.util.*;

public class Solution {
    HashSet<String> dict = new HashSet<String>();
    
    public String check(String[] arr, String word) {
        for (String str : arr) 
            dict.add(str);
        if (checkSeq(new StringBuffer(word))) return "true";
        return "false";
    }
    
    public boolean checkSeq(StringBuffer sb) {
        if (sb.length() == 1) return true;
        for (int i=0; i<=sb.length()-1; i++) {
            char cur = sb.charAt(i);
            sb.deleteCharAt(i);
            if (dict.contains(sb.toString())) {
                if (checkSeq(sb)) return true;
            }
            sb.insert(i, cur);
        }
        return false;
    }
    

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Solution sol = new Solution();
        System.out.println(sol.check(new String[]{"offce", "ofce", "ofc", "oc", "c"}, "office"));
    }

}