Java單鏈表、雙端鏈表、有序鏈表實現__Java

單鏈表：

insertFirst：在表頭插入一個新的連結點，時間複雜度為O(1)

deleteFirst：刪除表頭的連結點，時間複雜度為O(1)

有了這兩個方法，就可以用單鏈表來實現一個棧了，見http://blog.csdn.net/a19881029/article/details/22579759

find：尋找包含指定關鍵字的連結點，由於需要遍曆尋找，平均需要尋找N/2次，即O(N)

remove：刪除包含指定關鍵字的連結點，由於需要遍曆尋找，平均需要尋找N/2次，即O(N)

public class LinkedList {private class Data{private Object obj;private Data next = null;Data(Object obj){this.obj = obj;}}private Data first = null;public void insertFirst(Object obj){Data data = new Data(obj);data.next = first;first = data;}public Object deleteFirst() throws Exception{if(first == null)throw new Exception("empty!");Data temp = first;first = first.next;return temp.obj;}public Object find(Object obj) throws Exception{if(first == null)throw new Exception("LinkedList is empty!");Data cur = first;while(cur != null){if(cur.obj.equals(obj)){return cur.obj;}cur = cur.next;}return null;}public void remove(Object obj) throws Exception{if(first == null)throw new Exception("LinkedList is empty!");if(first.obj.equals(obj)){first = first.next;}else{Data pre = first;Data cur = first.next;while(cur != null){if(cur.obj.equals(obj)){pre.next = cur.next;}pre = cur;cur = cur.next;}}}public boolean isEmpty(){return (first == null);}public void display(){if(first == null)System.out.println("empty");Data cur = first;while(cur != null){System.out.print(cur.obj.toString() + " -> ");cur = cur.next;}System.out.print("\n");}public static void main(String[] args) throws Exception {LinkedList ll = new LinkedList();ll.insertFirst(4);ll.insertFirst(3);ll.insertFirst(2);ll.insertFirst(1);ll.display();ll.deleteFirst();ll.display();ll.remove(3);ll.display();System.out.println(ll.find(1));System.out.println(ll.find(4));}}

1 -> 2 -> 3 -> 4 -> 2 -> 3 -> 4 -> 2 -> 4 -> null4

雙端鏈表(不是雙向鏈表)：

與單向鏈表的不同之處在儲存有對最後一個連結點的引用(last)

insertFirst：在表頭插入一個新的連結點，時間複雜度O(1)

insertLast：在表尾插入一個新的連結點，時間複雜度O(1)

deleteFirst：刪除表頭的連結點，時間複雜度O(1)

deleteLast:：刪除表尾的連結點，由於只儲存了表尾的連結點，而沒有儲存表尾的前一個連結點(這裡就體現出雙向鏈表的優勢了)，所以在刪除表尾連結點時需要遍曆以找到表尾連結點的前一個連結點，需尋找N-1次，也就是O(N)

有了這幾個方法就可以用雙端鏈表來實現一個隊列了，http://blog.csdn.net/a19881029/article/details/22654121

public class FirstLastList {private class Data{private Object obj;private Data next = null;Data(Object obj){this.obj = obj;}}private Data first = null;private Data last = null;public void insertFirst(Object obj){Data data = new Data(obj);if(first == null)last = data;data.next = first;first = data;}public void insertLast(Object obj){Data data = new Data(obj);if(first == null){first = data;}else{last.next = data;}last = data;}public Object deleteFirst() throws Exception{  if(first == null)   throw new Exception("empty");  Data temp = first;  if(first.next == null)   last = null;  first = first.next;  return temp.obj; }public void deleteLast() throws Exception{if(first == null)throw new Exception("empty");if(first.next == null){first = null;last = null;}else{Data temp = first;while(temp.next != null){if(temp.next == last){last = temp;last.next = null;break;}temp = temp.next;}}}public void display(){if(first == null)System.out.println("empty");Data cur = first;while(cur != null){System.out.print(cur.obj.toString() + " -> ");cur = cur.next;}System.out.print("\n");}public static void main(String[] args) throws Exception {FirstLastList fll = new FirstLastList();fll.insertFirst(2);fll.insertFirst(1);fll.display();fll.insertLast(3);fll.display();fll.deleteFirst();fll.display();fll.deleteLast();fll.display();}}

1 -> 2 -> 1 -> 2 -> 3 -> 2 -> 3 -> 2 -> 

有序鏈表：鏈表中的資料按從小到大排列

public class SortedList {private class Data{private Object obj;private Data next = null;Data(Object obj){this.obj = obj;}}private Data first = null;public void insert(Object obj){Data data = new Data(obj);Data pre = null;Data cur = first;while(cur != null && (Integer.valueOf(data.obj.toString()).intValue() > Integer.valueOf(cur.obj.toString()).intValue())){pre = cur;cur = cur.next;}if(pre == null)first = data;elsepre.next = data;data.next = cur;}public Object deleteFirst() throws Exception{if(first == null)throw new Exception("empty!");Data temp = first;first = first.next;return temp.obj;}public void display(){if(first == null)System.out.println("empty");System.out.print("first -> last : ");Data cur = first;while(cur != null){System.out.print(cur.obj.toString() + " -> ");cur = cur.next;}System.out.print("\n");}public static void main(String[] args) throws Exception{SortedList sl = new SortedList();sl.insert(80);sl.insert(2);sl.insert(100);sl.display();System.out.println(sl.deleteFirst());sl.insert(33);sl.display();sl.insert(99);sl.display();}}

first -> last : 2 -> 80 -> 100 -> 2first -> last : 33 -> 80 -> 100 -> first -> last : 33 -> 80 -> 99 -> 100 -> 

表的插入和刪除平均需要比較N/2次，即O(N)，但是擷取最小資料項目只需O(1)，因為其始終處於表頭，對頻繁操作最小資料項目的應用，可以考慮使用有序鏈表實現，如：優先順序隊列

 

和數組相比，鏈表的優勢在於長度不受限制，並且在進行插入和刪除操作時，不需要移動資料項目，故儘管某些操作的時間複雜度與數組想同，實際效率上還是比數組要高很多

劣勢在於隨機訪問，無法像數組那樣直接通過下標找到特定的資料項目