Word Break II

Word Break II

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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"].

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在代码当中有英文的注释，关键是理解wordBreak的思想，其实是向前探测其数字是否符合要求。然后再用dfs递归，把所有符合结果的路径求解出来。

public class Solution {    // 19:10 -> 20:19 get accept    // first we should mark every outdoor of a character on a string. For example, the out dorr of 'c',the first character in s, is     //'t' and 's',there is no out door at a,because no word in dict is stars with a; and then, use 't' and 's' to find the ourdoors    // of these two characters; At the end, if the last character 'g' is reached, then it is possible to make a sentence by the dict.    // otherwise, no sentence is output.    // To output the sentences, we should use dfs   // 19:10 ->public ArrayList<String> wordBreak(String s, Set<String> dict) {//ArrayList<String> res;boolean isCent = false;int len = s.length(), lent = 0;ArrayList<ArrayList<Integer>> dp = new ArrayList<ArrayList<Integer>>();// I should initialize it at firstfor(int i=0;i<len+1;i++){dp.add(new ArrayList<Integer>());}//dp.set(0, new ArrayList<Integer>());dp.get(0).add(1);ArrayList<Integer> tmp = dp.get(0);String word, nw;for (int k = 0; k <= len; k++) {tmp = dp.get(k);if (tmp.size()!=0) {for (int j = 0; j < tmp.size(); j++) {//the int i = tmp.get(j);for (Iterator<String> it = dict.iterator(); it.hasNext();) {word = it.next();lent = word.length();if (i + lent <= len + 1) {    // index of string is less,but nw = s.substring(i - 1, i + lent - 1);if (nw.equals(word)) {    //I should judge whether the index is duplicated    // I must calculate the index of the string and the index of the dpif(!dp.get(i).contains(i+lent)){dp.get(i).add(i + lent);}if (i + lent == len + 1) {isCent = true;}}}}}}}if(isCent){dfs(dp, 1, s, new StringBuffer(), len);}return res;}ArrayList<String> res = new ArrayList<String>();void dfs(ArrayList<ArrayList<Integer>> dp, int index,String s, StringBuffer cent, int len) {ArrayList<Integer> tmp = null;tmp = dp.get(index);if (tmp.size()!=0) {for (int j = 0; j < tmp.size(); j++) {String st = s.substring(index - 1, tmp.get(j) - 1);// I must use another stringbufferStringBuffer centTmp = new StringBuffer(cent);centTmp.append(st);if (tmp.get(j) != len + 1) {centTmp.append(" ");dfs(dp,tmp.get(j), s,centTmp , len);} else {res.add(centTmp.toString());}}}return ;}}