［抄題］：

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

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"
 

[暴力解法]：

時間分析：

空間分析：

[優化後]：

時間分析：

空間分析：

［奇葩輸出條件］：

［奇葩corner case］：

［思維問題］：

不知道怎麽取單詞前半截：.substring都忘了，實在是太弱了。

［英文數據結構或算法，為什麽不用別的數據結構或算法］：

［一句話思路］：

［輸入量］：空： 正常情況：特大：特小：程序裏處理到的特殊情況：異常情況（不合法不合理的輸入）：

［畫圖］：

［一刷］：

substring包左不包右，所以i需要 i <= word.length多加一位

［二刷］：

［三刷］：

［四刷］：

［五刷］：

[五分鐘肉眼debug的結果]：

［總結］：

取前半截用substring，而且右邊界的i不包，要包就要加<=i的等號

［復雜度］：Time complexity: O(n) Space complexity: O(n)

［算法思想：叠代/遞歸/分治/貪心］：

［關鍵模板化代碼］：

［其他解法］：

［Follow Up］：

［LC給出的題目變變變］：

[代碼風格] ：

[是否頭一次寫此類driver funcion的代碼] ：

[潛臺詞] ：

class Solution {
    public String replaceWords(List<String> dict, String sentence) {
        //corner case
      if (dict == null || sentence.length() == 0) 
        return "";
      //initialization: set
      Set<String> set = new HashSet<String>();
      
      //put all the words into set
      for (int i = 0; i < dict.size(); i++) {
        set.add(dict.get(i));
      }
      
      //append the new result
      StringBuilder sb = new StringBuilder();
      String[] words = sentence.split("\\s+");
      for (String word : words) {
        String prefix = "";
        for (int i = 1; i <= word.length(); i++) {
          prefix = word.substring(0, i);
          if (set.contains(prefix)) break;
        }
        sb.append(" " + prefix);
      }
      
      //return
      return sb.deleteCharAt(0).toString();
    }
}

648. Replace Words 替換成為原來的單詞