648. Replace Words

In English, we have a concept called root, which can be followed by some other words to form another longer word - let's call this word successor. For example, the root an, followed by other, which can form another word another.

Now, given a dictionary consisting of many roots and a sentence. You need to replace all the successor in the sentence with the root forming it. If a successor has many roots can form it, replace it with the root with the shortest length.

You need to output the sentence after the replacement.

Example 1:

Input: dict = ["cat", "bat", "rat"]sentence = "the cattle was rattled by the battery"Output: "the cat was rat by the bat"

Note:

1. The input will only have lower-case letters.
2. 1 <= dict words number <= 1000
3. 1 <= sentence words number <= 1000
4. 1 <= root length <= 100
5. 1 <= sentence words length <= 1000

題意:

給定一個句子，還有一組辭典，將句子中含有辭典的詞進行替換(若辭典是句子中某個詞簡寫也需要替換)

例如:

Input: dict = ["cat", "bat", "rat"]sentence = "the cattle was rattled by the battery"Output: "the cat was rat by the bat"

題解:

** 需要把字典中所有詞存入HashSet，以提高查找效率**

先將句子的每個詞以" "分開，成一個數組，然後歷遍該數組中的每個詞，並將該詞由前往後進行簡寫枚舉，例如:

abcd -> a, ab, abc, abcd

若枚舉的詞符合字典中某個詞時，則進行替換，歷遍所有詞後，進行答案拼裝

package LeetCode.Medium;import java.util.HashSet;import java.util.List;import java.util.Set;public class ReplaceWords {    public String replaceWords(List<String> dict, String sentence) {        if(dict == null || dict.size() == 0 || sentence == null || sentence.equals("") || sentence.length() == 0){            return "";        }                //利用HashSet來做辭典，避免超時的問題(效率較高)        Set<String> dict_set = new HashSet<String>();                //將dict所有結果存入HashSet        dict_set.addAll(dict);                //以空白來切割        String[] words = sentence.split(" ");                for(int i = 0; i < words.length; i ++) {            String word = words[i];            //將字符串進行縮寫的枚舉(從前面枚舉至後面)            for(int j = 0; j <= word.length(); j ++) {                String sub_word = word.substring(0, j);                //若縮寫有在辭典中則進行替換                if(dict_set.contains(sub_word) == true) {                    words[i] = sub_word;                    break;                }            }        }                //組查答案        String result = "";        for(int i = 0; i < words.length; i ++) {            result += words[i] + " ";        }                //別忘了最後一個空格要去掉        return result.substring(0, result.length() - 1);    }}