[英]How to find Intersections in two singly linked lists
I am writing an program in which i have to set up data structure dictionary(singly linked list) with words alphabetically ordered(words that appear in sentence in a text document with document ids). 我正在编写一个程序,其中我必须设置数据结构字典(单链表),按字母顺序排列单词(出现在带有文档ID的文本文档中的句子中的单词)。 and find which words appear in more than one document so the professor wants us to do an intersection.
并找出哪些单词出现在多个文档中,以便教授希望我们做一个交集。 I am really confused on how to do the intersection.
我真的很困惑如何做交叉。 I have everything else(Which I believe is correct).
我有其他一切(我相信这是正确的)。 Here is my code(I have added my intersect algorithm, but it is clearly not working and I followed the professors algorithm[she never shows us an example]):
这是我的代码(我添加了我的交叉算法,但它显然不起作用,我遵循教授算法[她从未向我们展示过一个例子]):
public class dictionary
{
//variables
dNode head;
int size;
//constructor
public dictionary()
{
head = null;
size = 0;
}
//addFirst method
public void addFirst(dNode s)
{
s.setNext(head);
head = s;
size++;
}
public void addLast(dNode s)
{
if ( head == null )
{
head = s;
}
else
{
s.setNext(null);
dNode w = head;
while ( w.getNext() != null )
{
w = w.getNext();
}
w.setNext(s);
}
size++;
}
//toString Method
public String toString()
{
String w = "";
dNode s = head;
while ( s != null )
{
w += s + "\n";
s = s.getNext();
}
return w;
}
//intersection method
public String intersection(pNode head, dNode head) {
int left = posting.head;
int right = dictionary.head;
int result = new dictionary();
while (left != null && right != null) {
if (dID.left < dID.right) {
left = left.next;
else if (dID.left > dID.right)
right = right.next;
else
left = left.next;
right = right.next;
result.push(left.data() );
}
}
return result;
}
}
public class dNode
{
//variables
String sent;
posting post;
dNode nextNode;
//constructor
public dNode(String sent, posting post, dNode nextNode)
{
this.sent = sent;
this.post = post;
this.nextNode = nextNode;
}
//returns element of this node
public String getSent() {
return sent;
}
//retunrs the next node of this node
public dNode getNext() {
return nextNode;
}
//modifier methods
//sets elements of this node.
public void setSent(String newSent) {
sent = newSent;
}
//sets the next node of this node
public void setNext( dNode newNext) {
nextNode = newNext;
}
//toString method
public String toString()
{
return "Sentence and Posting: \n" + sent + "\n" + post;
}
}
public class pNode {
//variables
int dID;
String word;
int occurence;
pNode next;
//constructor
public pNode(int dID, String word, int occurence, pNode next)
{
this.dID = dID;
this.word = word;
this.occurence = occurence;
this.next = next;
}
//return element of this node
public String getWord() {
return word;
}
//Returns the next node of this node
public pNode getNext() {
return next;
}
//Modifier methods
//set the words of this node
public void setWord(String newWord) {
word = newWord;
}
//sets the next node of this node
public void setNext(pNode newNext){
next = newNext;
}
//toString method
public String toString() {
return "Document ID, Word, Occurence: \n " + dID + ", "
+ word + ", " + occurence;
}
}
public class posting
{
//variables
pNode head;
int size;
//constructor
public posting()
{
head = null;
size = 0;
}
//addFirst method
public void addFirst(pNode s)
{
s.setNext(head);
head = s;
size++;
}
//addLast method
public void addLast(pNode s)
{
if ( head == null )
{
head = s;
}
else
{
s.setNext(null);
pNode w = head;
while ( w.getNext() != null )
{
w = w.getNext();
}
w.setNext(s);
}
size++;
}
//toString method
public String toString()
{
String w = "";
pNode s = head;
while ( s != null)
{
w += s + "\n";
s = s.getNext();
}
return w;
}
}
import java.io.*;
import java.util.*;
public class testFile
{
public static void main (String[] args) throws FileNotFoundException
{
File filename = new File("/export/home/hawkdom2/s0878044/CS503/assignment2/sentences.txt");
Scanner scan = new Scanner(filename);
dictionary Dictionary = new dictionary();
while ( scan.hasNextLine() )
{
String sentence = scan.nextLine();
String[] word = sentence.split(" ");
//first element is document id
int dID = Integer.parseInt( word[0] );
//insertion sort
for ( int i = 2; i < word.length; i++ )
{
for ( int j = i; j > 1; j-- )
{
if ( word[j].compareTo( word[j-1] ) > 0 )
{
String switchs = word[j];
word[j] = word[j-1];
word[j-1] = switchs;
}
}
}
//integer array count
int[] count = new int[word.length];
for ( int i = 1; i < word.length; i++)
{
for ( int j = 1; j < word.length; j++)
{
if (word[i].equalsIgnoreCase( word[j] ) )
{
count[i]++;
}
}
}
posting posts = new posting();
for ( int i = 1; i < word.length; i++ )
{
if ( (i > 1 ) && (word[i].equalsIgnoreCase( word[i-1] ) ) )
continue;
else
{
posts.addFirst(new pNode(dID, word[i], count[i], null) );
}
}
Dictionary.addLast(new dNode(sentence, posts, null) );
}
//print out output
System.out.println(Dictionary);
}
}
This is the sentences file: 这是句子文件:
1 a rose is a rose
2 John chased a cat and the cat chased John
3 cats are mammals but mammals are not cats
4 beavers build dams but i know a beaver that does not
5 my dog chased a cat and the cat attacked my dog
6 my dog likes cats but my cat dislikes dogs
7 my dog likes roses but roses dislike my dog
8 my cat dislikes roses but roses like my cat
9 red roses are not my favorite roses
10 my favorite roses are pink roses
If I could get some insight on how to intersect the two linked lists(or if there is anything else wrong with my program) I would really greatly appreciate it. 如果我能够了解如何交叉两个链接列表(或者如果我的程序有任何其他错误),我会非常感激。 I have been sick for the last week and my professor refuses to help me on what I missed(apparently I am not a serious programmer if I don't come to class when I 'm sick).
我上周病了,我的教授拒绝帮助我做错过的事情(显然,如果我生病时不上课,我不是一个认真的程序员)。 I really cannot stand the way this professor teaches this class because she doesn't give us any examples of the programs(and the very few she does give us always have errors).
我真的不能忍受这位教授教授这门课程的方式,因为她没有给我们任何程序的例子(而且她给我们的极少数总是有错误)。 She also just gives us algorithms and she's already stated, they are not always correct.
她也只是给我们算法,她已经说过,但它们并不总是正确的。 I used to love programming but she has really turned me off on it and all I am trying to do now is get at least a C so I can just switch over to IT.
我曾经喜欢编程,但她真的让我失望了,我现在要做的就是至少得到一个C所以我可以切换到IT。 I would really appreciate if someone can help me, I am desperate to just get done with this class and not have to take this professor ever again.
如果有人可以帮助我,我真的很感激,我非常渴望完成这门课程而不必再接受这位教授。
I adding an intersect method but am still receiving all these errors: 7 errors found: File: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line: 86] Error: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:86: illegal start of expression File: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line: 86] Error: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:86: ';' 我添加了一个交叉方法,但仍然收到所有这些错误:找到7个错误:文件:/export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line:86]错误:/ export / home / hawkdom2 / s0878044 /CS503/assignment2/testFile.java:86:非法启动表达式文件:/export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line:86]错误:/ export / home / hawkdom2 / s0878044 / CS503 /assignment2/testFile.java:86:';' expected File: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line: 86] Error: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:86: not a statement File: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line: 86] Error: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:86: ';'
预期文件:/export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line:86]错误:/export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:86:不是声明文件: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line:86]错误:/export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:86:';' expected File: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line: 86] Error: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:86: not a statement File: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line: 86] Error: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:86: ';'
预期文件:/export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line:86]错误:/export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:86:不是声明文件: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line:86]错误:/export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:86:';' expected File: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line: 96] Error: /export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:96: 'else' without 'if'
预期文件:/export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java [line:96]错误:/export/home/hawkdom2/s0878044/CS503/assignment2/testFile.java:96:'其他'没有'如果'
public static void findIntersection(LLNode head1, LLnode head2)
{
HashSet<LLNode> hs= new HashSet<>();
HashSet<LLNode> hs2 = new HashSet<>();
LLNode currentNode1 = head1;
while(currentNode.getNext()!=null)
{
hs.add(currentNode);
currentNode1 = currentNode1.getNext();
}
LLNode currentNode2 = head2;
while(currentNode2.getNext()!=null)
{
if(hs1.contains(currentNode2)){
hs2.add(currentNode2);
}
}
Intersecting two sorted lists is easy. 相交两个排序列表很容易。
Start with a pointer to the first node in each list. 从指向每个列表中第一个节点的指针开始。 Let's call them
left
and right
. 让我们称他们为
left
和right
。 Create a new empty list, let's call it result
. 创建一个新的空列表,让我们称之为
result
。 Now you loop, comparing the data stored at the left
and right
nodes: 现在你循环,将存储在数据
left
和right
节点:
left
is less, advance left
. left
的数据较少,则left
前进。 right
is less, advance right
. right
的数据较少,则right
前进。 result
and advance both left
and right
. result
和推进两left
和right
。 Your loop continues until you read the end of either left
or right
. 你的循环继续,直到你读到
left
或right
的结尾。 Now you have intersected the two lists ( ie the result
list contains only the elements that appear in both left
and right
). 现在您已经交叉了两个列表( 即
result
列表仅包含left
right
出现的元素)。
function intersect( list1, list2 )
left <- list1.head
right <- list2.head
result <- new list
while left != null and right != null
if left.data < right.data
left <- left.next
elseif left.data > right.data
right <- right.next
else
left <- left.next
right <- right.next
result.push(left.data)
end if
end
return result
end function
For the best speeds, either store a tail
pointer in your list (so that addLast
is quick), or always add on the front (so your result is reverse-sorted) and then reverse the list afterwards (a simple operation with linear time-complexity). 为了获得最佳速度,可以在列表中存储
tail
指针(以便addLast
快速),或者始终在前面添加(因此您的结果是反向排序的)然后反转列表(使用线性时间的简单操作 -复杂)。
My version to find intersection of two linked list goes like below: 1. Iterate through first linked list and add element in IdentityHashMap as key. 我的版本找到两个链表的交集如下:1。迭代第一个链表并在IdentityHashMap中添加元素作为键。 2. Iterate through second linked list and go for containsKey check.
2.迭代第二个链表并进行containsKey检查。 If true then node is intersecting.
如果为true,则节点相交。
Time Complexity: O(n+m) where n = size of first list, m= size of second list Space Complexity: O(n) 时间复杂度:O(n + m)其中n =第一个列表的大小,m =第二个列表的大小空间复杂度:O(n)
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