hw3
smoosh相对来说比较复杂一些，尤其是最后一个数字向后比较的时候，很容易就丢了一个数，作业上说是用了14行码，我正好也是14行。后面squish开始忘记了比较要用equals不能用==，也是卡了半天，不好好审题。后面加了一些testcode检验这三个method。
import java.lang.reflect.Array; /* SList.java */ /** * The SList class is a singly-linked implementation of the linked list * abstraction. SLists are mutable data structures, which can grow at either * end. * * @author Kathy Yelick and Jonathan Shewchuk **/ public class SList { private SListNode head; private int size; /** * SList() constructs an empty list. **/ public SList() { size = 0; head = null; } /** * isEmpty() indicates whether the list is empty. * @return true if the list is empty, false otherwise. **/ public boolean isEmpty() { return size == 0; } /** * length() returns the length of this list. * @return the length of this list. **/ public int length() { return size; } /** * insertFront() inserts item "obj" at the beginning of this list. * @param obj the item to be inserted. **/ public void insertFront(Object obj) { head = new SListNode(obj, head); size++; } /** * insertEnd() inserts item "obj" at the end of this list. * @param obj the item to be inserted. **/ public void insertEnd(Object obj) { if (head == null) { head = new SListNode(obj); } else { SListNode node = head; while (node.next != null) { node = node.next; } node.next = new SListNode(obj); } size++; } /** * nth() returns the item at the specified position. If position < 1 or * position > this.length(), null is returned. Otherwise, the item at * position "position" is returned. The list does not change. * @param position the desired position, from 1 to length(), in the list. * @return the item at the given position in the list. **/ public Object nth(int position) { SListNode currentNode; if ((position < 1) || (head == null)) { return null; } else { currentNode = head; while (position > 1) { currentNode = currentNode.next; if (currentNode == null) { return null; } position--; } return currentNode.item; } } /** * smoosh() takes an array of ints. On completion the array contains * the same numbers, but wherever the array had two or more consecutive * duplicate numbers, they are replaced by one copy of the number. Hence, * after smoosh() is done, no two consecutive numbers in the array are the * same. * * Any unused elements at the end of the array are set to -1. * * For example, if the input array is [ 0 0 0 0 1 1 0 0 0 3 3 3 1 1 0 ], * it reads [ 0 1 0 3 1 0 -1 -1 -1 -1 -1 -1 -1 -1 -1 ] after smoosh() * completes. * * @param ints the input array. **/ public static void smoosh(int[] ints) { int k=0; int lengthOriginal=Array.getLength(ints); int lengthOf=lengthOriginal; for(int i=0;i<lengthOf;i++){ if(ints[i]==ints[i+1]){ for(int j=i+1;j<lengthOf;j++){ ints[j-1]=ints[j]; } lengthOf--; k++; if(i!=lengthOf-1)i--;} } for(int x=lengthOriginal-k;x<lengthOriginal;x++){ ints[x]=-1; } // Fill in your solution here. (Ours is fourteen lines long, not counting // blank lines or lines already present in this file.) } /** * squish() takes this list and, wherever two or more consecutive items are * equals(), it removes duplicate nodes so that only one consecutive copy * remains. Hence, no two consecutive items in this list are equals() upon * completion of the procedure. * * After squish() executes, the list may well be shorter than when squish() * began. No extra items are added to make up for those removed. * * For example, if the input list is [ 0 0 0 0 1 1 0 0 0 3 3 3 1 1 0 ], the * output list is [ 0 1 0 3 1 0 ]. * * IMPORTANT: Be sure you use the equals() method, and not the "==" * operator, to compare items. **/ public void squish() { SListNode a=head; while(a!=null){ if(a.next!=null){ if(a.item.equals(a.next.item)){ a.next=a.next.next; size--; }else a=a.next; }else a=a.next; }} /** * twin() takes this list and doubles its length by replacing each node * with two consecutive nodes referencing the same item. * * For example, if the input list is [ 3 7 4 2 2 ], the * output list is [ 3 3 7 7 4 4 2 2 2 2 ]. * * IMPORTANT: Do not try to make new copies of the items themselves. * Make new SListNodes, but just copy the references to the items. **/ public void twin() { SListNode original=head; SListNode copy; while(original!=null){ copy=new SListNode(original.item,original.next); original.next=copy; original=copy.next; }// Fill in your solution here. (Ours is seven lines long.) } /** * toString() converts the list to a String. * @return a String representation of the list. **/ public String toString() { int i; Object obj; String result = "[ "; SListNode cur = head; while (cur != null) { obj = cur.item; result = result + obj.toString() + " "; cur = cur.next; } result = result + "]"; return result; } /** * main() runs test cases on the SList class. Prints summary * information on basic operations and halts with an error (and a stack * trace) if any of the tests fail. **/ public static void main (String[] args) { int[] myArray={3,7,7,7,7,4,4,2,2,2,2,1}; smoosh(myArray); testEmpty(); testAfterInsertFront(); testAfterInsertEnd(); testsmoosh(); testsquish(); testtwin(); } private static void testsmoosh(){ int[] testInt={1,2,2,2,3,3,3,5,5,5}; System.out.println("Here is the original Array: "); for(int i=0;i<10;i++){ System.out.print(testInt[i]); } System.out.println(); System.out.println("Here is the Array after smoosh method: "); smoosh(testInt); for(int i=0;i<10;i++){ System.out.print(testInt[i]); } } private static void testsquish(){ SList testList1=new SList(); testList1.insertFront(1); testList1.insertFront(1); testList1.insertFront(2); testList1.insertFront(2); testList1.insertFront(3); testList1.insertFront(3); testList1.insertFront(3); System.out.println(); System.out.println("Here is a list of original construction: " + testList1.toString()); testList1.squish(); System.out.println("Here is a list of after squish method: " + testList1.toString()); } private static void testtwin(){ SList testList2=new SList(); testList2.insertFront(1); testList2.insertFront(2); testList2.insertFront(3); testList2.insertFront(4); testList2.insertFront(5); testList2.insertFront(5); System.out.println(); System.out.println("Here is a list of original construction: " + testList2.toString()); testList2.twin(); System.out.println("Here is a list after twin method: " + testList2.toString()); } /** * testEmpty() tests toString(), isEmpty(), length(), insertFront(), and * insertEnd() on an empty list. Prints summary information of the tests * and halts the program if errors are detected. **/ private static void testEmpty() { SList lst1 = new SList(); SList lst2 = new SList(); System.out.println(); System.out.println("Here is a list after construction: " + lst1.toString()); TestHelper.verify(lst1.toString().equals("[ ]"), "toString on newly constructed list failed"); System.out.println("isEmpty() should be true. It is: " + lst1.isEmpty()); TestHelper.verify(lst1.isEmpty() == true, "isEmpty() on newly constructed list failed"); System.out.println("length() should be 0. It is: " + lst1.length()); TestHelper.verify(lst1.length() == 0, "length on newly constructed list failed"); lst1.insertFront(new Integer(3)); System.out.println("Here is a list after insertFront(3) to an empty list: " + lst1.toString()); TestHelper.verify(lst1.toString().equals("[ 3 ]"), "InsertFront on empty list failed"); lst2.insertEnd(new Integer(5)); System.out.println("Here is a list after insertEnd(5) on an empty list: " + lst2.toString()); TestHelper.verify(lst2.toString().equals("[ 5 ]"), "insertEnd on empty list failed"); } /** * testAfterInsertFront() tests toString(), isEmpty(), length(), * insertFront(), and insertEnd() after insertFront(). Prints summary * information of the tests and halts the program if errors are detected. **/ private static void testAfterInsertFront() { SList lst1 = new SList(); lst1.insertFront(new Integer(3)); lst1.insertFront(new Integer(2)); lst1.insertFront(new Integer(1)); System.out.println(); System.out.println("Here is a list after insertFront 3, 2, 1: " + lst1.toString()); System.out.println("Here is a list after insertFront 3, 2, 1: " + lst1.toString()); TestHelper.verify(lst1.toString().equals("[ 1 2 3 ]"), "InsertFronts on non-empty list failed"); System.out.println("isEmpty() should be false. It is: " + lst1.isEmpty()); TestHelper.verify(lst1.isEmpty() == false, "isEmpty() after insertFront failed"); System.out.println("length() should be 3. It is: " + lst1.length()); TestHelper.verify(lst1.length() == 3, "length() after insertFront failed"); lst1.insertEnd(new Integer(4)); System.out.println("Here is the same list after insertEnd(4): " + lst1.toString()); TestHelper.verify(lst1.toString().equals("[ 1 2 3 4 ]"), "insertEnd on non-empty list failed"); } /** * testAfterInsertEnd() tests toString(), isEmpty(), length(), * insertFront(), and insertEnd() after insertEnd(). Prints summary * information of the tests and halts the program if errors are detected. **/ private static void testAfterInsertEnd() { SList lst1 = new SList(); lst1.insertEnd(new Integer(6)); lst1.insertEnd(new Integer(7)); System.out.println(); System.out.println("Here is a list after insertEnd 6, 7: " + lst1.toString()); System.out.println("isEmpty() should be false. It is: " + lst1.isEmpty()); TestHelper.verify(lst1.isEmpty() == false, "isEmpty() after insertEnd failed"); System.out.println("length() should be 2. It is: " + lst1.length()); TestHelper.verify(lst1.length() == 2, "length() after insertEndfailed"); lst1.insertFront(new Integer(5)); System.out.println("Here is the same list after insertFront(5): " + lst1.toString()); TestHelper.verify(lst1.toString().equals("[ 5 6 7 ]"), "insertFront after insertEnd failed"); } }
运行结果：
