斯坦福NLP解析器。如何拆分树？

Question

如果我从主页上举个例子：

The strongest rain ever recorded in India shut down 
the financial hub of Mumbai, snapped communication 
lines, closed airports and forced thousands of people 
to sleep in their offices or walk home during the night, 
officials said today.

斯坦福解析器：

LexicalizedParser lexicalizedParser = LexicalizedParser.loadModel("edu/stanford/nlp/models/lexparser/englishPCFG.ser.gz");

Tree parse = lexicalizedParser.parse(text);
TreePrint treePrint = new TreePrint("penn, typedDependencies");

treePrint.printTree(parse);

交付下面的树：

(ROOT
(S
  (S
    (NP
      (NP (DT The) (JJS strongest) (NN rain))
      (VP
        (ADVP (RB ever))
        (VBN recorded)
        (PP (IN in)
          (NP (NNP India)))))
    (VP
      (VP (VBD shut)
        (PRT (RP down))
        (NP
          (NP (DT the) (JJ financial) (NN hub))
          (PP (IN of)
            (NP (NNP Mumbai)))))
      (, ,)
      (VP (VBD snapped)
        (NP (NN communication) (NNS lines)))
      (, ,)
      (VP (VBD closed)
        (NP (NNS airports)))
      (CC and)
      (VP (VBD forced)
        (NP
          (NP (NNS thousands))
          (PP (IN of)
            (NP (NNS people))))
        (S
          (VP (TO to)
            (VP
              (VP (VB sleep)
                (PP (IN in)
                  (NP (PRP$ their) (NNS offices))))
              (CC or)
              (VP (VB walk)
                (NP (NN home))
                (PP (IN during)
                  (NP (DT the) (NN night))))))))))
  (, ,)
  (NP (NNS officials))
  (VP (VBD said)
    (NP-TMP (NN today)))
  (. .)))

我现在想拆分依赖于其结构的树以获取子句。所以在这个例子中，我想拆分树以获得以下部分：

• 印度有史以来最强的降雨
• 最强的降雨导致孟买金融中心关闭
• 最强的雨切断了通讯线路
• 最强降雨导致机场关闭
• 大雨迫使数千人睡在办公室
• 强降雨迫使数千人在夜间步行回家

所以第一个答案是使用递归算法打印所有根到叶的路径。

以下是我尝试过的代码：

public static void main(String[] args) throws IOException {
    LexicalizedParser lexicalizedParser = LexicalizedParser.loadModel("edu/stanford/nlp/models/lexparser/englishPCFG.ser.gz");

    Tree tree = lexicalizedParser.parse("In a ceremony that was conspicuously short on pomp and circumstance at a time of austerity, Felipe, 46, took over from his father, King Juan Carlos, 76.");

    printAllRootToLeafPaths(tree, new ArrayList<String>());
}

private static void printAllRootToLeafPaths(Tree tree, List<String> path) {
    if(tree != null) {
        if(tree.isLeaf()) {
            path.add(tree.nodeString());
        }

        if(tree.children().length == 0) {
            System.out.println(path);
        } else {
            for(Tree child : tree.children()) {
                printAllRootToLeafPaths(child, path);
            }
        }

        path.remove(tree.nodeString());
    }
}

当然，这段代码完全不符合逻辑，因为如果我只是将leaf添加到路径中，就永远不会有递归调用，因为leaf没有子对象。这里的问题是，所有真实的单词都是leaf，所以这个算法只会打印出单个单词，它们是leaf：

[The]
[strongest]
[rain]
[ever]
[recorded]
[in]
[India]
[shut]
[down]
[the]
[financial]
[hub]
[of]
[Mumbai]
[,]
[snapped]
[communication]
[lines]
[,]
[closed]
[airports]
[and]
[forced]
[thousands]
[of]
[people]
[to]
[sleep]
[in]
[their]
[offices]
[or]
[walk]
[home]
[during]
[the]
[night]
[,]
[officials]
[said]
[today]
[.]

Answer 1

看看打印二叉树或分裂二叉树中的所有根到叶路径：

• http://math-puzzles-computing.blogspot.nl/2011/02/splitting-binary-search-tree-at-given.html
• http://www.cs.cmu.edu/afs/cs/academic/class/15210-f11/www/lectures/18/lecture18.pdf
• http://digital.cs.usu.edu/~allan/DS/Notes/Ch19.pdf