LeetCode | Word Break II

原题描述：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"].

解题思路：

动态规划+DFS

实现代码：

/** * LeetCode | Word Break II * @author [e-mail] */public class Solution {List<String> records = new ArrayList<String>();public List<String> wordBreak(String s, Set<String> dict) {if (canBreak(s, dict)) {dfsSearch(s, dict, "");}return records;}private boolean canBreak(String s, Set<String> dict) {if (s == null || s.length() == 0 || dict == null || dict.size()==0)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] && dict.contains(s.substring(j, i))) {can[i] = true;break;}}}return can[len];}private void dfsSearch(String str, Set<String> dict, String result) {int len = str.length();if (len == 0) {records.add(result);}for (int i = 0; i <= len; i++) {String sub = str.substring(0,i);if(dict.contains(sub)){int curLen = result.length();if(!result.equals("")){result += " ";}result += sub;dfsSearch(str.substring(i), dict, result);result = result.substring(0, curLen);}}}}