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我正在做一些家庭作業問題，並且我陷入了對夫婦的困境。我很難理解交換列表中數據的最佳方法。使用虛假列表類
我應該使該方法reverse（），它使用LinkedIntList類（下面）。這是一個有限的列表類，所以我只能使用那裏的東西。
的點是取項目的列表
[1，2，3，4，5] 和反向他們 [5,4，3，2，1]
我想我的僞代碼將是
採取第一條數據並將其附加到列表中。 在原始大小上循環（因爲發生變化） 並取出0 處的棋子，然後將當前棋子添加到末尾0,1位置。
對於這樣的輸入： [1，8，19，4，17]
預期是這樣的： 前 - > [17] - > [4] - > [19] - > [8] - > [1]/
我的代碼獲取此： 前 - > [19] - > [4] - > [17] - > [8] - > [19] - > [1]/
不知道我做錯了什麼。
public void reverse(){
int x = this.size();
this.add(front.data);
for (int i = 0; i < x; i++){
this.remove(0);
this.add(this.size()-1, front.data);
}
}
// A LinkedIntList object can be used to store a list of integers.
public class LinkedIntList {
private ListNode front; // node holding first value in list (null if empty)
private String name = "front"; // string to print for front of list
// Constructs an empty list.
public LinkedIntList() {
front = null;
}
// Constructs a list containing the given elements.
// For quick initialization via Practice-It test cases.
public LinkedIntList(int... elements) {
this("front", elements);
}
public LinkedIntList(String name, int... elements) {
this.name = name;
if (elements.length > 0) {
front = new ListNode(elements[0]);
ListNode current = front;
for (int i = 1; i < elements.length; i++) {
current.next = new ListNode(elements[i]);
current = current.next;
}
}
}
// Constructs a list containing the given front node.
// For quick initialization via Practice-It ListNode test cases.
private LinkedIntList(String name, ListNode front) {
this.name = name;
this.front = front;
}
// Appends the given value to the end of the list.
public void add(int value) {
if (front == null) {
front = new ListNode(value, front);
} else {
ListNode current = front;
while (current.next != null) {
current = current.next;
}
current.next = new ListNode(value);
}
}
// Inserts the given value at the given index in the list.
// Precondition: 0 <= index <= size
public void add(int index, int value) {
if (index == 0) {
front = new ListNode(value, front);
} else {
ListNode current = front;
for (int i = 0; i < index - 1; i++) {
current = current.next;
}
current.next = new ListNode(value, current.next);
}
}
public boolean equals(Object o) {
if (o instanceof LinkedIntList) {
LinkedIntList other = (LinkedIntList) o;
return toString().equals(other.toString()); // hackish
} else {
return false;
}
}
// Returns the integer at the given index in the list.
// Precondition: 0 <= index < size
public int get(int index) {
ListNode current = front;
for (int i = 0; i < index; i++) {
current = current.next;
}
return current.data;
}
// Removes the value at the given index from the list.
// Precondition: 0 <= index < size
public void remove(int index) {
if (index == 0) {
front = front.next;
} else {
ListNode current = front;
for (int i = 0; i < index - 1; i++) {
current = current.next;
}
current.next = current.next.next;
}
}
// Returns the number of elements in the list.
public int size() {
int count = 0;
ListNode current = front;
while (current != null) {
count++;
current = current.next;
}
return count;
}
// Returns a text representation of the list, giving
// indications as to the nodes and link structure of the list.
// Detects student bugs where the student has inserted a cycle
// into the list.
public String toFormattedString() {
ListNode.clearCycleData();
String result = this.name;
ListNode current = front;
boolean cycle = false;
while (current != null) {
result += " -> [" + current.data + "]";
if (current.cycle) {
result += " (cycle!)";
cycle = true;
break;
}
current = current.__gotoNext();
}
if (!cycle) {
result += " /";
}
return result;
}
// Returns a text representation of the list.
public String toString() {
return toFormattedString();
}
// Returns a shorter, more "java.util.LinkedList"-like text representation of the list.
public String toStringShort() {
ListNode.clearCycleData();
String result = "[";
ListNode current = front;
boolean cycle = false;
while (current != null) {
if (result.length() > 1) {
result += ", ";
}
result += current.data;
if (current.cycle) {
result += " (cycle!)";
cycle = true;
break;
}
current = current.__gotoNext();
}
if (!cycle) {
result += "]";
}
return result;
}
// ListNode is a class for storing a single node of a linked list. This
// node class is for a list of integer values.
// Most of the icky code is related to the task of figuring out
// if the student has accidentally created a cycle by pointing a later part of the list back to an earlier part.
public static class ListNode {
private static final List<ListNode> ALL_NODES = new ArrayList<ListNode>();
public static void clearCycleData() {
for (ListNode node : ALL_NODES) {
node.visited = false;
node.cycle = false;
}
}
public int data; // data stored in this node
public ListNode next; // link to next node in the list
public boolean visited; // has this node been seen yet?
public boolean cycle; // is there a cycle at this node?
// post: constructs a node with data 0 and null link
public ListNode() {
this(0, null);
}
// post: constructs a node with given data and null link
public ListNode(int data) {
this(data, null);
}
// post: constructs a node with given data and given link
public ListNode(int data, ListNode next) {
ALL_NODES.add(this);
this.data = data;
this.next = next;
this.visited = false;
this.cycle = false;
}
public ListNode __gotoNext() {
return __gotoNext(true);
}
public ListNode __gotoNext(boolean checkForCycle) {
if (checkForCycle) {
visited = true;
if (next != null) {
if (next.visited) {
// throw new IllegalStateException("cycle detected in list");
next.cycle = true;
}
next.visited = true;
}
}
return next;
}
}
// YOUR CODE GOES HERE
}
您是否正在使用一個IDE來讓您逐步進行調試？它可以幫助你查看你的列表正在發生什麼。或者，在你的'for'循環中添加一個print語句（'System.out.println（toFormattedString（））'）來觀察列表的變化。 – 2012-08-02 07:02:22
它在練習網站上，所以我不能插入打印語句。這是我最大的抱怨，沒有調試代碼。 – hobbes131 2012-08-02 07:09:25
但是你知道代碼的細節，你剛剛發佈了它。如果你能抓住一個Java IDE（比如說[Eclipse]（http://www.eclipse.org/downloads/）），那麼把它放在一個新項目中並且玩一下就是一個簡單的任務。如果你掙扎，我們可以幫助你做到這一點。 – 2012-08-02 07:11:15