剑指offer——面试题18.1：删除链表中重复的节点

  1 // 面试题18（二）：删除链表中重复的结点
  2 // 题目：在一个排序的链表中，如何删除重复的结点？例如，在图3.4（a）中重复
  3 // 结点被删除之后，链表如图3.4（b）所示。
  4 
  5 #include <cstdio>
  6 #include "List.h"
  7 
  8 void DeleteDuplication(ListNode** pHead)
  9 {
 10     if(pHead == nullptr || *pHead == nullptr)
 11         return;
 12 
 13     ListNode* pPreNode = nullptr;
 14     ListNode* pNode = *pHead;
 15     while(pNode != nullptr)
 16     {
 17         ListNode *pNext = pNode->m_pNext;
 18         bool needDelete = false;
 19         if(pNext != nullptr && pNext->m_nValue == pNode->m_nValue)
 20             needDelete = true;
 21 
 22         if(!needDelete)
 23         {
 24             pPreNode = pNode;
 25             pNode = pNode->m_pNext;
 26         }
 27         else
 28         {
 29             int value = pNode->m_nValue;
 30             ListNode* pToBeDel = pNode;
 31             while(pToBeDel != nullptr && pToBeDel->m_nValue == value)
 32             {
 33                 pNext = pToBeDel->m_pNext;
 34 
 35                 delete pToBeDel;
 36                 pToBeDel = nullptr;
 37 
 38                 pToBeDel = pNext;
 39             }
 40 
 41             if(pPreNode == nullptr)
 42                 *pHead = pNext;
 43             else
 44                 pPreNode->m_pNext = pNext;
 45             pNode = pNext;
 46         }
 47     }
 48 }
 49 
 50 // ====================测试代码====================
 51 void Test(char* testName, ListNode** pHead, int* expectedValues, int expectedLength)
 52 {
 53     if(testName != nullptr)
 54         printf("%s begins: ", testName);
 55 
 56     DeleteDuplication(pHead);
 57 
 58     int index = 0;
 59     ListNode* pNode = *pHead;
 60     while(pNode != nullptr && index < expectedLength)
 61     {
 62         if(pNode->m_nValue != expectedValues[index])
 63             break;
 64 
 65         pNode = pNode->m_pNext;
 66         index++;
 67     }
 68 
 69     if(pNode == nullptr && index == expectedLength)
 70         printf("Passed.\n");
 71     else
 72         printf("FAILED.\n");
 73 }
 74 
 75 // 某些结点是重复的
 76 void Test1()
 77 {
 78     ListNode* pNode1 = CreateListNode(1);
 79     ListNode* pNode2 = CreateListNode(2);
 80     ListNode* pNode3 = CreateListNode(3);
 81     ListNode* pNode4 = CreateListNode(3);
 82     ListNode* pNode5 = CreateListNode(4);
 83     ListNode* pNode6 = CreateListNode(4);
 84     ListNode* pNode7 = CreateListNode(5);
 85 
 86     ConnectListNodes(pNode1, pNode2);
 87     ConnectListNodes(pNode2, pNode3);
 88     ConnectListNodes(pNode3, pNode4);
 89     ConnectListNodes(pNode4, pNode5);
 90     ConnectListNodes(pNode5, pNode6);
 91     ConnectListNodes(pNode6, pNode7);
 92 
 93     ListNode* pHead = pNode1;
 94 
 95     int expectedValues[] = { 1, 2, 5 };
 96     Test("Test1", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));
 97 
 98     DestroyList(pHead);
 99 }
100 
101 // 没有重复的结点
102 void Test2()
103 {
104     ListNode* pNode1 = CreateListNode(1);
105     ListNode* pNode2 = CreateListNode(2);
106     ListNode* pNode3 = CreateListNode(3);
107     ListNode* pNode4 = CreateListNode(4);
108     ListNode* pNode5 = CreateListNode(5);
109     ListNode* pNode6 = CreateListNode(6);
110     ListNode* pNode7 = CreateListNode(7);
111 
112     ConnectListNodes(pNode1, pNode2);
113     ConnectListNodes(pNode2, pNode3);
114     ConnectListNodes(pNode3, pNode4);
115     ConnectListNodes(pNode4, pNode5);
116     ConnectListNodes(pNode5, pNode6);
117     ConnectListNodes(pNode6, pNode7);
118 
119     ListNode* pHead = pNode1;
120 
121     int expectedValues[] = { 1, 2, 3, 4, 5, 6, 7 };
122     Test("Test2", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));
123 
124     DestroyList(pHead);
125 }
126 
127 // 除了一个结点之外其他所有结点的值都相同
128 void Test3()
129 {
130     ListNode* pNode1 = CreateListNode(1);
131     ListNode* pNode2 = CreateListNode(1);
132     ListNode* pNode3 = CreateListNode(1);
133     ListNode* pNode4 = CreateListNode(1);
134     ListNode* pNode5 = CreateListNode(1);
135     ListNode* pNode6 = CreateListNode(1);
136     ListNode* pNode7 = CreateListNode(2);
137 
138     ConnectListNodes(pNode1, pNode2);
139     ConnectListNodes(pNode2, pNode3);
140     ConnectListNodes(pNode3, pNode4);
141     ConnectListNodes(pNode4, pNode5);
142     ConnectListNodes(pNode5, pNode6);
143     ConnectListNodes(pNode6, pNode7);
144 
145     ListNode* pHead = pNode1;
146 
147     int expectedValues[] = { 2 };
148     Test("Test3", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));
149 
150     DestroyList(pHead);
151 }
152 
153 // 所有结点的值都相同
154 void Test4()
155 {
156     ListNode* pNode1 = CreateListNode(1);
157     ListNode* pNode2 = CreateListNode(1);
158     ListNode* pNode3 = CreateListNode(1);
159     ListNode* pNode4 = CreateListNode(1);
160     ListNode* pNode5 = CreateListNode(1);
161     ListNode* pNode6 = CreateListNode(1);
162     ListNode* pNode7 = CreateListNode(1);
163 
164     ConnectListNodes(pNode1, pNode2);
165     ConnectListNodes(pNode2, pNode3);
166     ConnectListNodes(pNode3, pNode4);
167     ConnectListNodes(pNode4, pNode5);
168     ConnectListNodes(pNode5, pNode6);
169     ConnectListNodes(pNode6, pNode7);
170 
171     ListNode* pHead = pNode1;
172 
173     Test("Test4", &pHead, nullptr, 0);
174 
175     DestroyList(pHead);
176 }
177 
178 // 所有结点都成对出现
179 void Test5()
180 {
181     ListNode* pNode1 = CreateListNode(1);
182     ListNode* pNode2 = CreateListNode(1);
183     ListNode* pNode3 = CreateListNode(2);
184     ListNode* pNode4 = CreateListNode(2);
185     ListNode* pNode5 = CreateListNode(3);
186     ListNode* pNode6 = CreateListNode(3);
187     ListNode* pNode7 = CreateListNode(4);
188     ListNode* pNode8 = CreateListNode(4);
189 
190     ConnectListNodes(pNode1, pNode2);
191     ConnectListNodes(pNode2, pNode3);
192     ConnectListNodes(pNode3, pNode4);
193     ConnectListNodes(pNode4, pNode5);
194     ConnectListNodes(pNode5, pNode6);
195     ConnectListNodes(pNode6, pNode7);
196     ConnectListNodes(pNode7, pNode8);
197 
198     ListNode* pHead = pNode1;
199 
200     Test("Test5", &pHead, nullptr, 0);
201 
202     DestroyList(pHead);
203 }
204 
205 // 除了两个结点之外其他结点都成对出现
206 void Test6()
207 {
208     ListNode* pNode1 = CreateListNode(1);
209     ListNode* pNode2 = CreateListNode(1);
210     ListNode* pNode3 = CreateListNode(2);
211     ListNode* pNode4 = CreateListNode(3);
212     ListNode* pNode5 = CreateListNode(3);
213     ListNode* pNode6 = CreateListNode(4);
214     ListNode* pNode7 = CreateListNode(5);
215     ListNode* pNode8 = CreateListNode(5);
216 
217     ConnectListNodes(pNode1, pNode2);
218     ConnectListNodes(pNode2, pNode3);
219     ConnectListNodes(pNode3, pNode4);
220     ConnectListNodes(pNode4, pNode5);
221     ConnectListNodes(pNode5, pNode6);
222     ConnectListNodes(pNode6, pNode7);
223     ConnectListNodes(pNode7, pNode8);
224 
225     ListNode* pHead = pNode1;
226 
227     int expectedValues[] = { 2, 4 };
228     Test("Test6", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));
229 
230     DestroyList(pHead);
231 }
232 
233 // 链表中只有两个不重复的结点
234 void Test7()
235 {
236     ListNode* pNode1 = CreateListNode(1);
237     ListNode* pNode2 = CreateListNode(2);
238 
239     ConnectListNodes(pNode1, pNode2);
240 
241     ListNode* pHead = pNode1;
242 
243     int expectedValues[] = { 1, 2 };
244     Test("Test7", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));
245 
246     DestroyList(pHead);
247 }
248 
249 // 结点中只有一个结点
250 void Test8()
251 {
252     ListNode* pNode1 = CreateListNode(1);
253 
254     ConnectListNodes(pNode1, nullptr);
255 
256     ListNode* pHead = pNode1;
257 
258     int expectedValues[] = { 1 };
259     Test("Test8", &pHead, expectedValues, sizeof(expectedValues) / sizeof(int));
260 
261     DestroyList(pHead);
262 }
263 
264 // 结点中只有两个重复的结点
265 void Test9()
266 {
267     ListNode* pNode1 = CreateListNode(1);
268     ListNode* pNode2 = CreateListNode(1);
269 
270     ConnectListNodes(pNode1, pNode2);
271 
272     ListNode* pHead = pNode1;
273 
274     Test("Test9", &pHead, nullptr, 0);
275 
276     DestroyList(pHead);
277 }
278 
279 // 空链表
280 void Test10()
281 {
282     ListNode* pHead = nullptr;
283 
284     Test("Test10", &pHead, nullptr, 0);
285 }
286 
287 int main(int argc, char* argv[])
288 {
289     Test1();
290     Test2();
291     Test3();
292     Test4();
293     Test5();
294     Test6();
295     Test7();
296     Test8();
297     Test9();
298     Test10();
299 
300     return 0;
301 }