腾讯三面的时候，叫我写了个哈希表，当时紧张没写好···结果跪了···
回来后粪发涂墙，赶紧写了一个！
什么都不说了···先让我到厕所里面哭一会···
%>_<%
果然现场发挥，以及基础扎实才是important的！
用链地址法解决冲突的哈希表（C语言，VS2008编写、测试）：
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <math.h>
4 #include <string.h>
5
6 struct node {
7 int count; // count the same value
8 char *value;
9 node *next;
10 };
11
12 // 使用链地址法解决冲突
13 struct hash_table {
14 int size; // table size
15 node **list; // 链表队列一条链为一个散列位置
16 };
17
18 //==================================================//
19 // declare
20
21 int hash_func(char *str, int tableSize);
22 hash_table *hash_table_init(int tableSize);
23 node *hash_table_new_node(char *str, int len);
24 int hash_table_insert(char *str, struct hash_table * head);
25 node *hash_table_find(char *str, struct hash_table * head);
26 void hash_table_clear(struct hash_table * head);
27 void hash_table_print(hash_table *head);
28
29 //==================================================//
30 // realize
31
32 // hash function: return the position of str in the hash table
33 int hash_func(char *str, int tableSize) {
34 unsigned int hashVal = 0;
35
36 while (*str != ‘\0‘)
37 hashVal += (hashVal << 5) + *str++;
38
39 return hashVal % tableSize;
40 }
41
42 // init & create hash table
43 hash_table *hash_table_init(int tableSize) {
44 hash_table *head;
45
46 head = (hash_table *)malloc(sizeof(hash_table));
47 if (NULL == head)
48 return NULL;
49 // 元素总数量尽可能为素数，以保证mod尽可能均匀
50 head->size = tableSize;
51
52 // 链表队列中，一条链为一个散列位置
53 head->list = (node **)malloc(sizeof(node *) * tableSize);
54
55 // initialize each hash list
56 int i;
57 for (i = 0; i < head->size; i++)
58 head->list[i] = NULL;
59
60 return head;
61 }
62
63 // return one new node
64 node *hash_table_new_node(char *str, int len) {
65 node *newNode = (node *)malloc(sizeof(node));
66 newNode->count = 1;
67 newNode->next = NULL;
68 newNode->value = (char *)malloc(len + 1);
69 memset(newNode->value, 0, len + 1);
70 memcpy(newNode->value, str, len);
71
72 return newNode;
73 }
74
75 // insert one node into hash table
76 int hash_table_insert(char *str, hash_table *head) {
77 int len = strlen(str);
78 // get str‘s position in the hash table
79 int pos = hash_func(str, head->size);
80
81 printf("[insert] %s at pos: %d\n", str, pos);
82
83 // locate list
84 node *q = head->list[pos], *p = head->list[pos];
85 for ( ; p != NULL; p = p->next) {
86 if (memcmp(p->value, str, len) == 0) {
87 p->count++; // found the same value, count+1
88 return pos;
89 }
90 q = p; // store the previous node
91 }
92
93 // if not found, then insert one new node
94 node *newNode = hash_table_new_node(str, len);
95 /*
96 //===================================================================//
97 // method 1:
98 // TODO: 如果是字符串不同，但是哈希值一样呢？？？貌似没考虑到这种情况
99 // insert into the head of list
100 newNode->next = head->list[pos];
101 head->list[pos] = newNode;
102 */
103 //===================================================================//
104 // method 2:
105 // insert into the tail of list
106 // 由于p指向了NULL，所以要插入链表尾的话，就必须增加一个变量q记录p前一个节点位置
107 if (NULL == q) {
108 newNode->next = head->list[pos];
109 head->list[pos] = newNode;
110 } else {
111 q->next = newNode;
112 newNode->next = NULL;
113 }
114
115 return pos;
116 }
117
118 // find the node which stored str & return it
119 node *hash_table_find(char *str, hash_table *head) {
120 if (NULL == head)
121 return NULL;
122
123 int pos = hash_func(str, head->size);
124 node *p = head->list[pos];
125
126 int len = strlen(str);
127
128 for ( ; p != NULL; p = p->next)
129 if (memcmp(p->value, str, len) == 0)
130 break;//return p; // found & return
131
132 return p; //return NULL;
133 }
134
135 // clear the whole hash table
136 void hash_table_clear(hash_table *head) {
137 if (NULL == head)
138 return;
139
140 node *p = NULL, *q = NULL;
141
142 int i;
143 for (i = 0; i < head->size; i++) {
144 p = head->list[i];
145 while (p != NULL) {
146 p->count = 0; // TODO: test
147 q = p->next;
148 // free value
149 if (p->value) {
150 free(p->value);
151 p->value = NULL;
152 }
153 // free current node
154 if (p) {
155 free(p);
156 p = NULL;
157 }
158 // point to next node
159 p = q;
160 }
161 }
162 // free list
163 if (head->list) {
164 free(head->list);
165 head->list = NULL;
166 }
167 // free head
168 if (head) {
169 free(head);
170 head = NULL;
171 }
172 }
173
174 // print the whole hash table
175 void hash_table_print(hash_table *head) {
176 if (NULL == head) {
177 printf("hash table is NULL! \n");
178 return;
179 }
180
181 int i;
182 node *p = NULL;
183
184 for ( i = 0; i < head->size; i++) {
185 p = head->list[i];
186 printf("//============list %d============//\n", i);
187 while (p != NULL) {
188 if (p->value)
189 printf("%s:%d ", p->value, p->count);
190 else
191 printf("(NULL):(0) ");
192 p = p->next;
193 }
194 printf("\n");
195 }
196 }
197
198 // test
199 int main() {
200 // create
201 hash_table *head = hash_table_init(10);
202
203 // insert
204 hash_table_insert("test 1", head);
205 hash_table_insert("test 2", head);
206 hash_table_insert("test 2", head);
207 hash_table_insert("test 3", head);
208 hash_table_insert("test 4", head);
209
210 hash_table_print(head);
211
212 // find
213 node *find = hash_table_find("test 2", head);
214 printf("\n[Find] %s:%d\n\n", find->value, find->count);
215
216 // clear
217 hash_table_clear(head);
218
219 hash_table_print(head);
220
221 // create
222 head = hash_table_init(6);
223
224 // insert
225 hash_table_insert("test 1", head);
226 hash_table_insert("test 2", head);
227 hash_table_insert("test 2", head);
228 hash_table_insert("test 3", head);
229 hash_table_insert("test 4", head);
230
231 hash_table_print(head);
232
233 return 0;
234 }
时间： 2024-10-30 02:00:39