leetcode — word-break-ii

import java.util.*;

/**
 * Source : https://oj.leetcode.com/problems/word-break-ii/
 *
 * Given a string s and a dictionary of words dict, add spaces in s to construct a sentence
 * where each word is a valid dictionary word.
 *
 * Return all such possible sentences.
 *
 * For example, given
 * s = "catsanddog",
 * dict = ["cat", "cats", "and", "sand", "dog"].
 *
 * A solution is ["cats and dog", "cat sand dog"].
 */
public class WordBreak2 {
    /**
     * 找到所有可能的分割方法，使得分割后的单词在dic中
     *
     * 使用DFS
     *
     * @param str
     * @param dic
     * @return
     */
    public String[] wordBreak (String str, Set<String> dic) {
        List<String> result = new ArrayList<String>();
        List<String> solution = new ArrayList<String>();
        recursion(str, dic, solution, result);
        return result.toArray(new String[solution.size()]);
    }

    private void recursion (String str, Set<String> dic, List<String> solution, List<String> result) {
        if (str.length() == 0 && solution.size() > 0) {
            StringBuffer stringBuffer = new StringBuffer();
            for (String word : solution) {
                stringBuffer.append(word);
                stringBuffer.append(" ");
            }
            result.add(stringBuffer.substring(0, stringBuffer.length()-1));
        }
        for (int i = 0; i < str.length(); i++) {
            if (dic.contains(str.substring(0, i+1))) {
                solution.add(str.substring(0, i+1));
                recursion(str.substring(i+1, str.length()), dic, solution, result);
                solution.remove(solution.size()-1);
            }
        }
    }

    public static void main(String[] args) {
        WordBreak2 wordBreak2 = new WordBreak2();
        String[] dicStr = new String[]{"cat", "cats", "and", "sand", "dog"};
        System.out.println(Arrays.toString(wordBreak2.wordBreak("catsanddog", new HashSet<String>(Arrays.asList(dicStr)))));
    }
}