leetcode 140. Word Break II ----- java

標籤：val   arraylist   str   res   div   possible   count   const   for   

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"].

 

139題的延伸題，需要的出所有結果。

 

1、遞迴，仍舊逾時。

public class Solution {    String[] result;    List list;    public List<String> wordBreak(String s, Set<String> wordDict) {        int len = s.length(),maxLen = 0;        result = new String[len];        list = new ArrayList<String>();        for( String str : wordDict ){            maxLen = Math.max(maxLen,str.length());        }        helper(s,0,wordDict,maxLen,0);        return list;        }    public void helper(String s,int pos,Set<String> wordDict,int maxLen,int count){        if( pos == s.length() ){            String str = result[0];            for( int i = 1 ; i<count-1;i++){                str =str+ " "+result[i];            }            if( count > 1)                str = str+" "+result[count-1];            list.add(str);        }        int flag = 0;        for( int i = pos;pos - i<maxLen && i<s.length();i++){            if( wordDict.contains( s.substring(pos,i+1) )){                result[count] = s.substring(pos,i+1);                helper(s,i+1,wordDict,maxLen,count+1);                flag = 1;            }        }        }}

 2、加入提前判斷是否存在答案（即上一題的結論）就可以了。

public class Solution {    String[] result;    List list;    public List<String> wordBreak(String s, Set<String> wordDict) {        int len = s.length(),maxLen = 0;        result = new String[len];        list = new ArrayList<String>();                for( String str : wordDict ){            maxLen = Math.max(maxLen,str.length());        }        boolean[] dp = new boolean[len];        for( int i = 0 ;i<len;i++){            for( int j = i;j>=0 && i-j<maxLen;j-- ){                if( ( j == 0 || dp[j-1] == true ) && wordDict.contains(s.substring(j,i+1)) ){                    dp[i] = true;                    break;                }            }        }        if( dp[len-1] == false)            return list;                helper(s,0,wordDict,maxLen,0);        return list;        }    public void helper(String s,int pos,Set<String> wordDict,int maxLen,int count){        if( pos == s.length() ){            String str = result[0];            for( int i = 1 ; i<count-1;i++){                str =str+ " "+result[i];            }            if( count > 1)                str = str+" "+result[count-1];            list.add(str);        }        int flag = 0;        for( int i = pos;pos - i<maxLen && i<s.length();i++){            if( wordDict.contains( s.substring(pos,i+1) )){                result[count] = s.substring(pos,i+1);                helper(s,i+1,wordDict,maxLen,count+1);                flag = 1;            }        }        }}

 

leetcode 140. Word Break II ----- java