原题：实现一个嵌套类DoubleNode用来构造双向链表，其中每个节点都含有一个指向前驱元素的引用和一个指向后续元素的引用(如果不存在则为NULL)。为以下任务实现若干静态方法：在表头插入结点、在表尾插入结点、在表头删除结点、在表尾删除结点、在指定结点之前插入新结点、在指定结点之后插入新结点、删除指定结点。
我写的代码里为了加强程序的模块化、将调用和实现分离，添加另外几个方法，并且没有使用静态方法。
构造类：
1 package com.lch.Chapter1_3; 2 3 import java.util.Iterator; 4 5 import edu.princeton.cs.algs4.StdOut; 6 7 /** 8 * 9 * @author Lucas.Li 10 * 11 * @param <Item> 12 * 13 * @Content 双向链表的构造 14 */ 15 public class BothwayLinkedListStack<Item> implements Iterable<Item> { 16 17 private int N; 18 private DoubleNode first; 19 private DoubleNode last; 20 21 /** 22 * 23 * @author Lucas.Li 构造嵌套类 24 * 25 */ 26 private class DoubleNode { 27 Item item; 28 DoubleNode next; 29 DoubleNode prev; 30 } 31 32 /** 33 * 34 * @return 链表大小 35 */ 36 public int size() { 37 return N; 38 } 39 40 /** 41 * 42 * @return 链表是否为空 43 */ 44 public boolean isEmpty() { 45 return N == 0; 46 } 47 48 /** 49 * 在表头添加元素 50 * 51 * @param item 52 */ 53 public void push(Item item) { 54 DoubleNode oldFirst = first; 55 first = new DoubleNode(); 56 first.item = item; 57 first.next = oldFirst; 58 first.prev = null; 59 if (N == 0) { 60 last = first; 61 } else { 62 oldFirst.prev = first; 63 } 64 N++; 65 } 66 67 /** 68 * 69 * @return 表头弹出的元素值 70 */ 71 public Item pop() { 72 if (N == 0) { 73 try { 74 throw new Exception("There is none on stack!"); 75 } catch (Exception e) { 76 // TODO Auto-generated catch block 77 e.printStackTrace(); 78 } 79 } 80 Item item = first.item; 81 first = first.next; 82 first.prev = null; 83 N--; 84 return item; 85 } 86 87 /** 88 * 表头添加元素 89 * 90 * @param item 91 */ 92 public void insertHead(Item item) { 93 DoubleNode node = new DoubleNode(); 94 node.item = item; 95 node.prev = null; 96 node.next = first; 97 first.prev = node; 98 first = new DoubleNode(); 99 first = node; 100 N++; 101 } 102 103 /** 104 * 表尾添加元素 105 * 106 * @param item 107 */ 108 public void insertTail(Item item) { 109 DoubleNode node = new DoubleNode(); 110 node.item = item; 111 node.prev = last; 112 node.next = null; 113 last.next = node; 114 last = new DoubleNode(); 115 last = node; 116 N++; 117 } 118 119 /** 120 * 指定结点前插入元素 121 * 122 * @param item 123 * @param node 124 */ 125 public void insertBeforeNode(Item item, DoubleNode node) { 126 if (isFirst(node)) { 127 insertHead(item); 128 N++; 129 } else { 130 DoubleNode newNode = new DoubleNode(); 131 newNode.item = item; 132 newNode.prev = node.prev; 133 newNode.next = node; 134 node.prev.next = newNode; 135 node.prev = newNode; 136 N++; 137 } 138 } 139 140 /** 141 * 指定结点后插入元素 142 * 143 * @param item 144 * @param node 145 */ 146 public void insertAfterNode(Item item, DoubleNode node) { 147 if (isLast(node)) { 148 insertTail(item); 149 N++; 150 } else { 151 DoubleNode newNode = new DoubleNode(); 152 newNode.item = item; 153 newNode.prev = node; 154 newNode.next = node.next; 155 node.next.prev = newNode; 156 node.next = newNode; 157 N++; 158 } 159 } 160 161 /** 162 * 删除指定结点 163 * @param node 164 */ 165 public void deleteNode(DoubleNode node){ 166 if (isFirst(node)){ 167 deleteHead(); 168 N--; 169 } else if (isLast(node)) { 170 deleteTail(); 171 N--; 172 } else { 173 node.next.prev = node.prev; 174 node.prev.next = node.next; 175 node.prev = null; 176 node.next = null; 177 N--; 178 } 179 } 180 181 /** 182 * 删除表头元素 183 */ 184 public void deleteHead() { 185 if (N == 0) { 186 try { 187 throw new Exception("There is none on stack!"); 188 } catch (Exception e) { 189 // TODO Auto-generated catch block 190 e.printStackTrace(); 191 } 192 } 193 first = first.next; 194 first.prev = null; 195 N--; 196 } 197 198 /** 199 * 删除表尾元素 200 */ 201 public void deleteTail() { 202 if (N == 0) { 203 try { 204 throw new Exception("There is none on stack!"); 205 } catch (Exception e) { 206 // TODO Auto-generated catch block 207 e.printStackTrace(); 208 } 209 } 210 last = last.prev; 211 last.next = null; 212 N--; 213 } 214 215 /** 216 * 217 * @param m 218 * @return 指定结点(从表头数起第m个结点) 219 */ 220 public DoubleNode getNode(int m) { 221 if (m > N) { 222 try { 223 throw new Exception("Not enough on stack! Return the last one!"); 224 } catch (Exception e) { 225 // TODO Auto-generated catch block 226 e.printStackTrace(); 227 } 228 return last; 229 } 230 DoubleNode node = new DoubleNode(); 231 node = first; 232 int i = 1; 233 while (i < m) { 234 node = node.next; 235 i++; 236 } 237 return node; 238 } 239 240 /** 241 * 242 * @param node 243 * @return 结点元素的值 244 */ 245 public Item getItem(DoubleNode node) { 246 return node.item; 247 } 248 249 /** 250 * 251 * @return 链表首结点 252 */ 253 public DoubleNode getFirst() { 254 return first; 255 } 256 257 /** 258 * 259 * @return 链表尾结点 260 */ 261 public DoubleNode getLast() { 262 return last; 263 } 264 265 /** 266 * 267 * @param node 268 * @return 判断结点是否为首结点 269 */ 270 public boolean isFirst(DoubleNode node) { 271 if (node.prev == null) { 272 return true; 273 } else { 274 return false; 275 } 276 } 277 278 /** 279 * 280 * @param node 281 * @return 判断结点是否为尾结点 282 */ 283 public boolean isLast(DoubleNode node) { 284 if (node.next == null) { 285 return true; 286 } else { 287 return false; 288 } 289 } 290 291 /** 292 * 遍历器 293 */ 294 @Override 295 public Iterator<Item> iterator() { 296 // TODO Auto-generated method stub 297 return new ListIterator(); 298 } 299 300 /** 301 * 扩展实现遍历器 302 * 303 * @author Administrator 304 * 305 */ 306 private class ListIterator implements Iterator<Item> { 307 308 private DoubleNode current = first; 309 310 @Override 311 public boolean hasNext() { 312 // TODO Auto-generated method stub 313 return current != null; 314 } 315 316 @Override 317 public Item next() { 318 // TODO Auto-generated method stub 319 Item item = current.item; 320 current = current.next; 321 return item; 322 } 323 324 @SuppressWarnings("unused") 325 public DoubleNode getCurrent() { 326 return current; 327 } 328 329 } 330 331 }
测试类：
1 package com.lch.MyTest; 2 3 import java.util.Iterator; 4 5 import com.lch.Chapter1_3.BothwayLinkedListStack; 6 import com.lch.Chapter1_3.LinkedListStack; 7 8 import edu.princeton.cs.algs4.StdOut; 9 10 /** 11 * 双向链表测试类 12 * @author Administrator 13 * 14 */ 15 public class DoubleNodeTest { 16 17 public static void init_01() { 18 BothwayLinkedListStack<String> blls = new BothwayLinkedListStack<String>(); 19 String[] strs = "abcdefg".split(""); 20 for (int i = 0; i < strs.length; i++) { 21 blls.push(strs[i]); 22 } 23 iteratorList(blls); 24 blls.insertHead("head"); 25 iteratorList(blls); 26 blls.insertTail("tail"); 27 iteratorList(blls); 28 blls.deleteHead(); 29 iteratorList(blls); 30 blls.deleteTail(); 31 iteratorList(blls); 32 blls.insertBeforeNode("before", blls.getNode(2)); 33 iteratorList(blls); 34 blls.insertAfterNode("after", blls.getNode(2)); 35 iteratorList(blls); 36 blls.deleteNode(blls.getNode(2)); 37 iteratorList(blls); 38 } 39 40 public static <Item> void iteratorList(BothwayLinkedListStack<Item> stack) { 41 Iterator<Item> iterator = stack.iterator(); 42 while (iterator.hasNext()) { 43 StdOut.print(iterator.next() + " "); 44 } 45 StdOut.println(); 46 } 47 48 public static void main(String[] args) { 49 init_01(); 50 } 51 52 }
结果：
