[LeetCode]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"].

先dp找到所有的路径，然后用深搜纪录所有结果。注意是否存在解决方案的判定。

public class Solution {Integer maxLen = -1;boolean prev[][];boolean f[];List<String> res = new ArrayList<>();List<String> path = new ArrayList<>();    public List<String> wordBreak(String s, Set<String> dict) {            Iterator<String> it = dict.iterator();        while(it.hasNext()){        maxLen = Math.max(it.next().length(),maxLen);        }        prev= new boolean[s.length()][maxLen+1];        f= new boolean[s.length()+1];        f[0] = true;        help(0,s,dict);        //判断是否存在解，不存在解的话调用genPath()会超时        if(f[s.length()]!=true)return res;        genPath(0,s,path,res);        return res;            }        private  void help(int start,String s, Set<String> dict){    for(int i=0;i<s.length();i++){    for(int j=i+1;j<=i+maxLen&&j<=s.length();j++){    String str = s.substring(i,j);    if(f[i]&&dict.contains(str)){    prev[i][j-i] = true;    f[j] = true;    }    }    }    }        private void genPath(int start,String s,List<String> path,List<String> res){    if(start==s.length()){StringBuilder sb = new StringBuilder();for(int i=0;i<path.size()-1;i++){sb.append(path.get(i)+" ");}sb.append(path.get(path.size()-1));res.add(sb.toString());}    for(int i=start+1;i<=s.length()&&i<=start+maxLen;i++){    if(prev[start][i-start]){    path.add(s.substring(start,i));    genPath(i,s,path,res);    path.remove(path.size()-1);    }    }    }}