不记得是大一还是大二开的《数据结构》，当时可真是可爱，按照我当时的想法就是这东西有什么用，目光短浅的我。。。学什么都是学这个有什么用啊？典型的一枚功利分子。
后来读了一些读物，了解到 数据结构 就是如何表示 数据 的一种形式，计算机什么是计算，计算就是机械式的信息处理，信息是什么，信息就是数字，一列列的 binary number。
但是在处理信息时，考虑到了 效率，人就是懒，不懒不进步。把信息以一种什么样的形式交给计算机，就可以立马得出 result。这就用到了 数据结构 + 算法，虽然算法还没看。。。
在GeeksforGeeks学DS，我也真的是有意思。
Linked list 单链表，优点和缺点也已经写过了。
1 #include<stdlib.h> 2 #include<stdio.h> 3 4 //Linked list from FengSF 5 struct node 6 { 7 int data; 8 struct node * next; 9 }; 10 void printList(struct node * n) 11 { 12 while(NULL != n) 13 { 14 printf("%d\t", n->data); 15 n = n->next; 16 } 17 18 } 19 //在头结点之前插入新节点 20 void push(struct node ** head_ref, int new_data) 21 { 22 struct node * new_node = (struct node*) malloc(sizeof(struct node)); 23 24 new_node->data = new_data; 25 new_node->next = (*head_ref); 26 (*head_ref) = new_node; 27 } 28 //链表中间插入新节点 29 void afterAdd(struct node * prev_node, int new_data) 30 { 31 if(NULL == prev_node) 32 { 33 printf("ERROR!"); 34 return; 35 } 36 37 struct node * new_node = (struct node *) malloc (sizeof(struct node)); 38 new_node->data = new_data; 39 new_node->next = prev_node->next; 40 prev_node->next = new_node; 41 } 42 //在尾节点之后插入新节点 43 void endAdd(struct node ** head_ref, int new_data) 44 { 45 struct node * new_node = (struct node *) malloc (sizeof(struct node)); 46 struct node * last = (*head_ref); 47 new_node->data = new_data; 48 new_node->next = NULL; 49 50 if(NULL == (*head_ref)) 51 { 52 (*head_ref) = new_node; 53 return ; 54 } 55 56 while(NULL != last->next) 57 { 58 last = last->next; 59 } 60 61 last->next = new_node; 62 } 63 //移除结点通过data 64 void deleteElementByKey(struct node ** head_ref, int key) 65 { 66 struct node * temp = (*head_ref), * pre; 67 68 if(NULL != temp && temp->data == key) 69 { 70 (*head_ref) = temp->next; 71 free(temp); 72 return ; 73 } 74 75 while(NULL != temp && temp->data != key) 76 { 77 pre = temp; 78 temp = temp->next; 79 } 80 if(NULL == temp) 81 { 82 printf("The element isn`t exist!"); 83 return ; 84 } 85 pre->next = temp->next; 86 free(temp); 87 } 88 //移除结点通过位置 89 void deleteElementByPosition(struct node ** head_ref, int position) 90 { 91 struct node * temp = (*head_ref), * pre; 92 int listLength = linkedListLength(temp); 93 94 if(position < 0 && position > listLength) 95 { 96 printf("The position is error!"); 97 return ; 98 } 99 temp = (*head_ref); 100 if(NULL != temp && 1 == position) 101 { 102 (*head_ref) = temp->next; 103 free(temp); 104 return ; 105 } 106 int times = 0; 107 while(NULL != temp && (position-1) != times) 108 { 109 pre = temp; 110 temp = temp->next; 111 times++; 112 } 113 if(NULL == temp) 114 { 115 printf("The position %d isn`t exist! and the linkedlist`s length is %d\n", position, listLength); 116 return ; 117 } 118 pre->next = temp->next; 119 free(temp); 120 } 121 //销毁链表 122 void destroyLinkedlist(struct node ** head_ref) 123 { 124 struct node * current = (*head_ref), *next; 125 126 while(NULL != current) 127 { 128 next = current->next; 129 free(current); 130 current = next; 131 } 132 133 (*head_ref) = NULL; 134 } 135 //链表的长度 136 int linkedListLength(struct node * head_ref) 137 { 138 int length = 0; 139 140 while(NULL != head_ref) 141 { 142 length++; 143 head_ref = head_ref->next; 144 } 145 146 return length; 147 } 148 //搜索元素值是否存在于链表中 149 int searchElement(struct node * head_ref, int key) 150 { 151 int judge; 152 153 while(NULL != head_ref && key != head_ref->data) 154 { 155 head_ref = head_ref->next; 156 } 157 if(NULL == head_ref) 158 { 159 judge = 0; 160 return judge; 161 } 162 163 judge = 1; 164 return judge; 165 } 166 //通过结点的位置获取结点 167 struct node * getNodeByPosition(struct node * head_ref, int position) 168 { 169 int length = linkedListLength(head_ref); 170 171 if(NULL == head_ref) 172 { 173 printf("\n The linked list no elements"); 174 } 175 if(position <= 0 && position > length) 176 { 177 printf("\n Error "); 178 return ; 179 } 180 int times = 0; 181 while(NULL != head_ref && times != position-1) 182 { 183 head_ref = head_ref->next; 184 times++; 185 } 186 return head_ref; 187 } 188 //获取倒数的元素 189 struct node * getNodeByPositionFromLast(struct node * head_ref, int position) 190 { 191 int length = linkedListLength(head_ref); 192 193 if(NULL == head_ref) 194 { 195 printf("\n The linked list no elements"); 196 } 197 if(-1 == boolPosition(head_ref, position)) 198 { 199 printf("\nError"); 200 } 201 202 for(int i = 0; i < length-position; i++) 203 { 204 head_ref = head_ref->next; 205 } 206 return head_ref; 207 } 208 //判断所求位置是否正确 209 int boolPosition(struct node * head_ref, int position) 210 { 211 int length = linkedListLength(head_ref); 212 213 if(position <= 0 && position > length) 214 { 215 return -1; 216 } 217 218 return 1; 219 } 220 //返回中间的元素 221 int findMiddleElement(struct node * head_ref) 222 { 223 int length = linkedListLength(head_ref)/2 + 1; 224 //int length1 = (length%2 == 0) ? length/2+1 : length/2+1; 225 226 //printf("\nlength1 = %d and length = %d", length1, length); 227 struct node * temp = getNodeByPosition(head_ref, length); 228 return temp->data; 229 } 230 int findMiddleElement_2(struct node * head_ref) 231 { 232 struct node * fast_ptr = head_ref; 233 struct node * slow_ptr = head_ref; 234 235 if(NULL == head_ref) 236 { 237 printf("\n ERROR"); 238 return -1; 239 } 240 while(NULL != fast_ptr && NULL != fast_ptr->next) 241 { 242 fast_ptr = fast_ptr->next->next; 243 slow_ptr = slow_ptr->next; 244 } 245 246 return slow_ptr->data; 247 } 248 int findMiddleElement_3(struct node * head_ref) 249 { 250 struct node * mid = head_ref; 251 int counter = 0; 252 253 while(NULL != head_ref) 254 { 255 if(counter & 1) 256 { 257 mid = mid->next; 258 } 259 260 counter++; 261 head_ref = head_ref->next; 262 } 263 264 return mid->data; 265 } 266 //不用递归返回元素个数 267 int countWhithoutRecursion(struct node * head_ref, int key) 268 { 269 int counter = 0; 270 int length = linkedListLength(head_ref); 271 272 if(-1 == headIsNULL(head_ref)) 273 { 274 printf("The linked list is null!"); 275 return -1; 276 } 277 for(int i = 0; (i < length && head_ref != NULL); i++) 278 { 279 if(key == head_ref->data) 280 { 281 counter++; 282 head_ref = head_ref->next; 283 } 284 else 285 { 286 head_ref = head_ref->next; 287 } 288 } 289 290 return counter; 291 } 292 /*void sortList(struct node ** head_ref) 293 { 294 struct node * temp = (*head_ref); 295 struct node * pre = NULL; 296 297 if(-1 == headIsNULL(*head_ref)) 298 { 299 printf("ERROR!"); 300 return ; 301 } 302 else 303 { 304 if(temp->data > temp->next->data) 305 { 306 temp->next = temp->next->next; 307 temp->next->next = temp; 308 (*head_ref) = temp; 309 } 310 temp = (*head_ref); 311 312 while(temp != NULL) 313 { 314 if(temp->data <= temp->next->data) 315 { 316 pre = temp; 317 temp = temp->next; 318 } 319 else 320 { 321 pre->next = temp->next; 322 temp->next = temp->next->next; 323 temp->next->next = temp; 324 temp = 325 } 326 } 327 } 328 }*/ 329 //判断是否为循环链表 330 int isCircular(struct node * head_ref) 331 { 332 if(NULL == head_ref) 333 { 334 return 1; 335 } 336 337 struct node * temp = head_ref->next; 338 339 while(temp != NULL && temp != head_ref) 340 { 341 temp = temp->next; 342 } 343 344 return (temp == head_ref) ? 1 : -1; 345 } 346 static int counter = 0; 347 //通过递归返回节点个数 348 int countWithRecursion(struct node * head_ref, int key) 349 { 350 if(NULL == head_ref) 351 { 352 return counter; 353 } 354 if(key == head_ref) 355 { 356 counter++; 357 } 358 countWhithoutRecursion(head_ref->next, key); 359 } 360 //判断是否为空链表 361 int headIsNULL(struct node * head_ref) 362 { 363 return (NULL == head_ref)? -1 : 1; 364 } 365 int main(void) 366 { 367 struct node * first = NULL; 368 struct node * second = NULL; 369 struct node * third = NULL; 370 371 first = (struct node *)malloc(sizeof(struct node)); 372 second = (struct node *)malloc(sizeof(struct node)); 373 third = (struct node *)malloc(sizeof(struct node)); 374 375 first->data = 1; 376 first->next = second; 377 378 second->data = 2; 379 second->next = third; 380 381 third->data = 3; 382 third->next = NULL; 383 384 endAdd(&first, 100); 385 push(&first, 99); 386 push(&first, 88); 387 push(&first, 77); 388 push(&first, 11); 389 push(&first, 66); 390 push(&first, 99); 391 push(&first, 88); 392 push(&first, 77); 393 push(&first, 11); 394 push(&first, 66); 395 //destroyLinkedlist(&first); 396 int length = linkedListLength(first); 397 printList(first); 398 printf("\nThe length of singly linked list is %d", length); 399 printf("\n The value of bool is %d", searchElement(first, 44)); 400 struct node * temp = getNodeByPosition(first, 4); 401 printf("\n The node`s value is %d", temp->data); 402 struct node * temp1 = getNodeByPositionFromLast(first, 2); 403 printf("\n The node`s value is %d", temp1->data); 404 printf("\n The middle element of linked list is %d", findMiddleElement(first)); 405 printf("\n The middle element of linked list is %d", findMiddleElement_2(first)); 406 printf("\n The middle element of linked list is %d", findMiddleElement_3(first)); 407 printf("\n Count the %d is %d", 88, countWhithoutRecursion(first, 88)); 408 printf("\n Count the %d is %d", 88, countWhithoutRecursion(first, 88)); 409 printf("\n Count the %d is %d", 88, countWhithoutRecursion(first, 11)); 410 if(0 < isCircular(first)) 411 { 412 printf("\nThe linked list is circularLinked list!------%d"); 413 } 414 else 415 { 416 printf("\nThe linked list isn`t circularLinked list!"); 417 } 418 return 0; 419 }
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