我正在制作一个双链表，它将“盒子”存放在一个有5个架子的仓库里。每个货架都不能容纳一个链表，该链表保存着该货架上的“箱子”。我有一个问题，当我尝试移动其中一个盒子时，我会将盒子添加到另一个架子上，但当我尝试从旧架子上取下盒子时，我的程序将只删除我刚刚添加到新盒子中的盒子架。下面是我的货架类代码，用于设置列表和我的仓库代码，其中存在我遇到问题的moveOneBox方法。
package assignment2;
public class Warehouse{
protected Shelf[] storage;
protected int nbShelves;
public Box toShip;
public UrgentBox toShipUrgently;
static String problem = "problem encountered while performing the operation";
static String noProblem = "operation was successfully carried out";
public Warehouse(int n, int[] heights, int[] lengths){
this.nbShelves = n;
this.storage = new Shelf[n];
for (int i = 0; i < n; i++){
this.storage[i]= new Shelf(heights[i], lengths[i]);
}
this.toShip = null;
this.toShipUrgently = null;
}
public String printShipping(){
Box b = toShip;
String result = "not urgent : ";
while(b != null){
result += b.id + ", ";
b = b.next;
}
result += "\n" + "should be already gone : ";
b = toShipUrgently;
while(b != null){
result += b.id + ", ";
b = b.next;
}
result += "\n";
return result;
}
public String print(){
String result = "";
for (int i = 0; i < nbShelves; i++){
result += i + "-th shelf " + storage[i].print();
}
System.out.println(result);
return result;
}
public void clear(){
toShip = null;
toShipUrgently = null;
for (int i = 0; i < nbShelves ; i++){
storage[i].clear();
}
}
/**
* initiate the merge sort algorithm
*/
public void sort(){
mergeSort(0, nbShelves -1);
}
/**
* performs the induction step of the merge sort algorithm
* @param start
* @param end
*/
protected void mergeSort(int start, int end) {
int middle;
if (start < end) {
middle = (start + end) / 2;
mergeSort(start, middle);
mergeSort(middle + 1, end);
merge(start, middle, end);
}
}
/**
* performs the merge part of the merge sort algorithm
* @param start
* @param mid
* @param end
*/
protected void merge(int start, int mid, int end){
int sizeOfLeft = mid - start + 1;
int sizeOfRight = end - mid;
Shelf left_Array[] = new Shelf[sizeOfLeft];
Shelf right_Array[] = new Shelf[sizeOfRight];
for(int i = 0; i < sizeOfLeft; i++) {
left_Array[i] = storage[start + i];
}
for(int j = 0; j < sizeOfRight; j++) {
right_Array[j] = storage[mid+1+j];
}
int i = 0;
int j = 0;
int k = start;
while(i < sizeOfLeft && j < sizeOfRight) {
if(left_Array[i].height <= right_Array[j].height) {
storage[k] = left_Array[i];
i++;
}
else {
storage[k] = right_Array[j];
j++;
}
k++;
}
while(i < sizeOfLeft) {
storage[k] = left_Array[i];
i++;
k++;
}
while(j < sizeOfRight) {
storage[k] = right_Array[j];
j++;
k++;
}
}
/**
* Adds a box is the smallest possible shelf where there is room available.
* Here we assume that there is at least one shelf (i.e. nbShelves >0)
* @param b
* @return problem or noProblem
*/
public String addBox (Box b){
int i = 0, shelf_Space_Available = 0, lowest_Shelf = 1001, index_Lowest_Shelf = -1;
while(i < nbShelves) {
if(b.height <= storage[i].height && b.length <= storage[i].availableLength) {
shelf_Space_Available = storage[i].height - b.height;
if(shelf_Space_Available < lowest_Shelf) {
lowest_Shelf = shelf_Space_Available;
index_Lowest_Shelf = i;
}
}
i++;
}
if(index_Lowest_Shelf >= 0) {
System.out.println(b.id+" adding to shelf"+index_Lowest_Shelf);
storage[index_Lowest_Shelf].addBox(b);
System.out.println(index_Lowest_Shelf);
print();
return noProblem;
}
else {
return problem;
}
}
/**
* Adds a box to its corresponding shipping list and updates all the fields
* @param b
* @return problem or noProblem
*/
public String addToShip (Box b){
//System.out.println("Add to ship has box: "+b.id);
if(b instanceof UrgentBox) {
if(toShipUrgently == null) {
toShipUrgently = (UrgentBox)b;
return noProblem;
}
else {
Box temp = toShipUrgently;
while(temp != null) {
temp = temp.next;
}
temp = b;
temp.next = null;
return noProblem;
}
}
else if(b instanceof Box) {
if(toShip == null) {
toShip = b;
return noProblem;
}
else {
//System.out.println(b.id+" is an instance of box. Adding to box list");
b.next = toShip;
toShip.previous = b;
toShip = b;
}
}
//System.out.println(b.id+" did not work");
return problem;
}
/**
* Find a box with the identifier (if it exists)
* Remove the box from its corresponding shelf
* Add it to its corresponding shipping list
* @param identifier
* @return problem or noProblem
*/
public String shipBox (String identifier){
Box grabber = null;
int i = 0;
while((grabber = storage[i].removeBox(identifier)) == null) {
i++;
if(i >= nbShelves) {
break;
}
}
if(grabber != null) {
addToShip(grabber);
return noProblem;
}
return problem;
}
/**
* if there is a better shelf for the box, moves the box to the optimal shelf.
* If there are none, do not do anything
* @param b
* @param position
*/
public void moveOneBox (Box b, int position){
/*Box check;
System.out.println("Removing "+b.id+" from shelf #"+position);
check = storage[position].removeBox(b.id);
System.out.println(check.id);
print();
if(check.id.equals(b.id)){
addBox(b);
}
else{
System.out.println("Box not moved -- not found.");
}*/
String problemOrNoProblem = addBox(b);
System.out.println("Removing "+b.id+" from shelf #"+position);
if(problemOrNoProblem.contentEquals(noProblem)){
Box check = storage[position].removeBox(b.id);
System.out.println(check.id+" removed from shelf "+position);
}
}
/**
* reorganize the entire warehouse : start with smaller shelves and first box on each shelf.
*/
public void reorganize (){
Box compare;
print();
for(int i = 0; i < nbShelves; i++) {
compare = storage[i].firstBox;
while(compare != null) {
moveOneBox(compare, i);
compare = compare.next;
}
}
}
}
和我的货架类代码。
package assignment2;
public class Shelf {
protected int height;
protected int availableLength;
protected int totalLength;
protected Box firstBox;
protected Box lastBox;
public Shelf(int height, int totalLength){
this.height = height;
this.availableLength = totalLength;
this.totalLength = totalLength;
this.firstBox = null;
this.lastBox = null;
}
protected void clear(){
availableLength = totalLength;
firstBox = null;
lastBox = null;
}
public String print(){
String result = "( " + height + " - " + availableLength + " ) : ";
Box b = firstBox;
while(b != null){
result += b.id + ", ";
b = b.next;
}
result += "\n";
return result;
}
/**
* Adds a box on the shelf. Here we assume that the box fits in height and length on the shelf.
* @param b
*/
public void addBox(Box b){
if(firstBox == null) {
b.next = null;
b.previous = null;
firstBox = b;
lastBox = b;
}
else {
lastBox.next = b;
b.previous = lastBox;
b.next = null;
lastBox = b;
}
System.out.println(b.id+" added");
availableLength = availableLength - lastBox.length;
}
/**
* If the box with the identifier is on the shelf, remove the box from the shelf and return that box.
* If not, do not do anything to the Shelf and return null.
* @param identifier
* @return
*/
public Box removeBox(String identifier){
Box temp = firstBox;
while(temp != null) {
if(temp.id.equals(identifier)) {
if(temp.next != null && temp.previous != null) {
temp.previous.next = temp.next;
temp.next.previous = temp.previous;
temp.next = null;
temp.previous = null;
System.out.println("Running normal removal "+identifier);
}
else if(temp.next == null && temp.previous == null) {
firstBox = null;
lastBox = null;
System.out.println("Running only 1 box "+identifier);
}
else if(temp.next == null && temp.previous != null) {
lastBox = temp.previous;
temp.previous = null;
lastBox.next = null;
System.out.println("Running last box "+identifier+" previous box is "+lastBox.id);
}
else if(temp.next != null && temp.previous == null) {
firstBox = temp.next;
temp.next = null;
firstBox.previous = null;
System.out.println("Running first box "+identifier);
}
availableLength = availableLength + temp.length;
return temp;
}
//System.out.println("Next box");
temp = temp.next;
}
System.out.println("No box "+identifier);
return null;
}
}
非常感谢任何人给我的帮助/提示，谢谢。
你的moveOneBox应该是这样的：
public void moveOneBox (Box b, int position){
Box check;
System.out.println("Removing "+b.id+" from shelf #"+position);
check = storage[position].removeBox(b.id);
System.out.println(check.id);
for(int i = 0; i< nbShelves ; i++) {
if(storage[i].height >= b.height && storage[i].availableLength >= b.length) {
storage[i].addBox(b);
break;
}
}
}
你的reorganize应该是这样的：
public void reorganize (){
Box compare;
print();
for(int i = 0; i < nbShelves; i++) {
compare = storage[i].firstBox;
while(compare != null) {
Box nextCompare = compare.next;
moveOneBox(compare, i);
compare = nextCompare;
}
}
}