学习笔记之程序员面试攻略(第2版)

程序员面试攻略_百度百科

http://baike.baidu.com/link?url=egiDevITF7mxrqaIMf804VbBrCWIwaBsL5QgGZPgb_TfdhRuBZaYXcnLoL-sD7AjX-US4vhW0Zc7eZjWNAYOx_

第4章　　链表

更新头指针。
bool insertInFront1(ListNode *pInHead, int inVal)只是对*pInHead进行值传递，然后在函数内更新了头指针的“本地拷贝”。
要更新指针可以有两种方式：bool insertInFront2(ListNode **pInHead, int inVal)就是传入了头指针的指针，ListNode *insertInFront3(ListNode *pInHead, int inVal)则是直接返回新的头指针。
注意只是传入头指针的话，直接传递pHead。如果是头指针的指针，则是&pHead。

  1 #include <iostream>
  2 using namespace std;
  3 
  4 struct ListNode 
  5 {
  6        int val;
  7        ListNode *next;
  8        ListNode(int x = 0) : val(x), next(NULL) {}
  9 };
 10  
 11 class Solution 
 12 {
 13 public:
 14     void PrintList(ListNode *inListNode)
 15     {
 16          if (inListNode != NULL) {
 17             cout << inListNode->val << endl;
 18             PrintList(inListNode->next);
 19          } else
 20             cout << "NULL\n" << endl;
 21     }
 22 
 23     bool insertInFront1(ListNode *pInHead, int inVal)
 24     {
 25          cout << "Entry bool insertInFront1(ListNode *pInHead, int inVal)\n" << endl;
 26          
 27          if (pInHead == NULL) return false;
 28                   
 29          ListNode *pNewElem = new ListNode;
 30          pNewElem->val = inVal;
 31          pInHead = pNewElem; // Incorret!
 32 
 33          cout << "pNewElem = " << pNewElem << endl;
 34          cout << "PrintList(pNewElem)" << endl;
 35          PrintList(pNewElem);
 36 
 37          cout << "pInHead = " << pInHead << endl;
 38          cout << "PrintList(pInHead)" << endl;
 39          PrintList(pInHead);
 40 
 41          return true;
 42     }
 43 
 44     bool insertInFront2(ListNode **pInHead, int inVal)
 45     {
 46          cout << "Entry bool insertInFront2(ListNode **pInHead, int inVal)\n" << endl;
 47          
 48          if (pInHead == NULL) return false;
 49                   
 50          ListNode *pNewElem = new ListNode;
 51          pNewElem->val = inVal;
 52          *pInHead = pNewElem; // Correctly updates head
 53 
 54          cout << "pNewElem = " << pNewElem << endl;
 55          cout << "PrintList(pNewElem)" << endl;
 56          PrintList(pNewElem);
 57 
 58          cout << "pInHead = " << pInHead << endl;
 59          cout << "PrintList(pInHead)" << endl;
 60          PrintList(*pInHead);
 61 
 62          return true;
 63     }
 64 
 65     ListNode *insertInFront3(ListNode *pInHead, int inVal)
 66     {
 67          cout << "Entry ListNode *insertInFront3(ListNode *pInHead, int inVal)\n" << endl;
 68          
 69          if (pInHead == NULL) return false;
 70                   
 71          ListNode *pNewElem = new ListNode;
 72          pNewElem->val = inVal;
 73 
 74          cout << "pNewElem = " << pNewElem << endl;
 75          cout << "PrintList(pNewElem)" << endl;
 76          PrintList(pNewElem);
 77 
 78          cout << "pInHead = " << pInHead << endl;
 79          cout << "PrintList(pInHead)" << endl;
 80          PrintList(pInHead);
 81 
 82          return pNewElem;  // Correctly updates head
 83     }
 84 };
 85 
 86 int main ()
 87 {
 88     Solution testSolution;
 89     int value = 5;
 90  
 91     ListNode* pHead = new ListNode(1);
 92 
 93     cout << "Test bool insertInFront1(ListNode *pInHead, int inVal)\n" << endl;
 94     // Print Head node
 95     cout << "pHead = " << pHead << endl;
 96     if (pHead != NULL)
 97        cout << "pHead->val = " << pHead->val << endl;
 98     cout << endl;
 99 
100     // Print Linkedlist
101     cout << "PrintList(pHead)" << endl;
102     testSolution.PrintList(pHead);        
103     
104     bool flag = testSolution.insertInFront1(pHead, value);
105     cout << "testSolution.insertInFront1(pHead, value) = " << flag << "\n" << endl;
106 
107     // Print Head node
108     cout << "pHead = " << pHead << endl;
109     if (pHead != NULL)
110        cout << "pHead->val = " << pHead->val << endl;
111     cout << endl;
112 
113     // Print Linkedlist
114     cout << "PrintList(pHead)" << endl;
115     testSolution.PrintList(pHead);        
116 
117     delete pHead;
118     pHead = NULL;
119             
120     cout << "Test bool insertInFront2(ListNode **pInHead, int inVal)\n" << endl;
121 
122     pHead = new ListNode(2);
123 
124     // Print Head node
125     cout << "pHead = " << pHead << endl;
126     if (pHead != NULL)
127        cout << "pHead->val = " << pHead->val << endl;
128     cout << endl;
129 
130     // Print Linkedlist
131     cout << "PrintList(pHead)" << endl;
132     testSolution.PrintList(pHead);        
133     
134     flag = testSolution.insertInFront2(&pHead, value);
135     cout << "testSolution.insertInFront2(&pHead, value) = " << flag << "\n" << endl;
136 
137     // Print Head node
138     cout << "pHead = " << pHead << endl;
139     if (pHead != NULL)
140        cout << "pHead->val = " << pHead->val << endl;
141     cout << endl;
142 
143     // Print Linkedlist
144     cout << "PrintList(pHead)" << endl;
145     testSolution.PrintList(pHead);        
146 
147     delete pHead;
148     pHead = NULL;
149 
150     cout << "Test ListNode *insertInFront3(ListNode *pInHead, int inVal)\n" << endl;
151 
152     pHead = new ListNode(3);
153 
154     // Print Head node
155     cout << "pHead = " << pHead << endl;
156     if (pHead != NULL)
157        cout << "pHead->val = " << pHead->val << endl;
158     cout << endl;
159 
160     // Print Linkedlist
161     cout << "PrintList(pHead)" << endl;
162     testSolution.PrintList(pHead);        
163     
164     pHead = testSolution.insertInFront3(pHead, value);
165 
166     // Print Head node
167     cout << "pHead = " << pHead << endl;
168     if (pHead != NULL)
169        cout << "pHead->val = " << pHead->val << endl;
170     cout << endl;
171 
172     // Print Linkedlist
173     cout << "PrintList(pHead)" << endl;
174     testSolution.PrintList(pHead);        
175 
176     delete pHead;
177     pHead = NULL;
178 
179     getchar();
180     
181     return 0;
182 }

View Code

遍历链表时，要不断的检查它的末尾。 E.g. head != NULL
删除链表
注意删除顺序，指针移动赋值

 1 #include <iostream>
 2 using namespace std;
 3 
 4 struct ListNode 
 5 {
 6        int val;
 7        ListNode *next;
 8        ListNode(int x = 0) : val(x), next(NULL) {}
 9 };
10  
11 class Solution 
12 {
13 public:
14     void PrintList(ListNode *inListNode)
15     {
16          if (inListNode != NULL) {
17             cout << inListNode->val << endl;
18             PrintList(inListNode->next);
19          } else
20             cout << "NULL" << endl;
21     }
22     
23     // Assign in ptr of the head ptr
24     void DeleteList(ListNode **pInHead)
25     {
26          ListNode *pDel = *pInHead;
27          
28          while (pDel != NULL)
29          {
30                // Reserve the address of the next node
31                ListNode *pNext = pDel->next;              
32                // Delete the current node
33                delete pDel;
34                pDel = NULL;
35                // Move to the next node
36                pDel = pNext;
37          }
38 
39          // Set head to NULL         
40          *pInHead = NULL;
41     }
42 };
43 
44 int main ()
45 {
46     Solution testSolution;
47     int count = 10;
48     
49     ListNode *pHead = NULL;
50     ListNode *pCur = NULL;
51     
52     for (int i = 0; i < count; i ++)
53     {
54         ListNode *pTemp = new ListNode(i);
55         
56         if (i == 0)
57             pHead = pCur = pTemp;
58         else {
59             pCur->next = pTemp;
60             pCur = pCur->next; // pCur->next == pTemp
61         }
62     }
63     
64     // Print Head       
65     cout << "pHead = " << pHead << endl;
66     if (pHead != NULL)
67        cout << "pHead->val = " << pHead->val << endl;
68     cout << endl;
69     
70     // Print Linkedlist
71     cout << "PrintList(pHead)" << endl;
72     testSolution.PrintList(pHead);        
73 
74     cout << "Test DeleteList(pHead)\n" << endl;     
75     testSolution.DeleteList(&pHead);
76     
77     // Print Head       
78     cout << "pHead = " << pHead << endl;
79     if (pHead != NULL)
80        cout << "pHead->val = " << pHead->val << endl;
81     cout << endl;
82     
83     // Print Linkedlist
84     cout << "PrintList(pHead)" << endl;
85     testSolution.PrintList(pHead);        
86 
87     getchar();
88     
89     return 0;
90 }

View Code

posted on 2016-06-15 22:32 浩然119 阅读(278) 评论(0) 编辑收藏举报