/** Train the generator by adding the sourceText */
@Override
public void train(String sourceText) {
// TODO: Implement this method
String splitOn = "[\\s.]+";
String[] words = sourceText.split(splitOn);
String prev = starter;
for (String word : words) {
ListNode tomodify = null;
ListIterator<ListNode> iter = wordList.listIterator();
while (iter.hasNext()) {
ListNode node = iter.next();
if (node.getWord().equals(prev)) {
tomodify = node;
break;
}
}
if (tomodify == null) {
tomodify = new ListNode(prev);
wordList.add(tomodify);
}
// add w to the targeted ListNode
tomodify.addNextWord(word);
prev = word;
}
}
/*
Markov Text Generation depends on an initial source text to mimic.
This method takes in String to train the Markov Text Generator.
*/
@Override
public void train(String sourceText) {
// TODO: Implement this method
if (sourceText == null || sourceText.length() == 0) {
return;
}
String[] words = sourceText.split("[ ]+"); // 注意test cases中，words之间可能有多个空格
starter = words[0];
for (int i = 1; i < words.length; i++) {
String crtWord = words[i];
ListNode prevNode = isExist(words[i - 1], wordList);
if (prevNode == null) {
prevNode = new ListNode(words[i - 1]);
wordList.add(prevNode);
}
prevNode.addNextWord(crtWord);
}
// setup the "starter" word and to make sure the last word also points to the start word.
ListNode prevNode = isExist(words[words.length - 1], wordList);
if (prevNode == null) {
prevNode = new ListNode(words[words.length - 1]);
wordList.add(prevNode);
}
prevNode.addNextWord(starter);
}
private ListNode findNode(String key) {
for (ListNode n : wordList) {
if (n.getWord().equals(key)) {
return n;
}
}
return null;
}
// Can be helpful for debugging
@Override
public String toString() {
String toReturn = "";
for (ListNode n : wordList) {
toReturn += n.toString();
}
return toReturn;
}
// helper function
private ListNode isExist(String crtWord, List<ListNode> wordList) {
int size = wordList.size();
for (int i = 0; i < size; i++) {
ListNode node = wordList.get(i);
if (node.getWord().equals(crtWord)) {
return node;
}
}
return null;
}
/** Generate the number of words requested. */
@Override
public String generateText(int numWords) {
// TODO: Implement this method
if (wordList.size() == 0) {
return "";
}
String text = "";
String current = starter;
for (int i = 0; i < numWords; i++) {
ListNode curnode = findNode(current);
if (curnode == null) {
curnode = findNode(starter);
}
String nexttext = curnode.getRandomNextWord(rnGenerator);
text = text + nexttext + " ";
current = nexttext;
}
return text;
}
/*
The goal of Markov Text Generation is to be able to generate text which resembles the source in a reasonable way.
The method generateText returns such text as a String of words, the length of which is determined by numWords.
*/
@Override
public String generateText(int numWords) {
// TODO: Implement this method
if (numWords < 0) {
throw new IllegalArgumentException("Illegal Argument");
}
if (numWords == 0) {
return "";
}
StringBuilder sb = new StringBuilder();
String crtWord = starter;
sb.append(crtWord + " ");
numWords--; // 先减去starter word占据的一个
while (numWords-- > 0) {
ListNode node = isExist(crtWord, wordList);
String next = node.getRandomNextWord(rnGenerator);
sb.append(next + " ");
crtWord = next;
}
return sb.toString();
}