└── lists.c


/lists.c:
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  1 | #include <stdio.h>
  2 | #include <stdlib.h>
  3 | 
  4 | typedef struct {
  5 |     void *next;
  6 |     int data;
  7 | } Node;
  8 | 
  9 | Node *head = NULL;
 10 | 
 11 | // add a node to the list
 12 | Node *addNode(int data)
 13 | {
 14 |     Node *new = NULL;
 15 |     // two cases:
 16 | 
 17 |     // if the list is empty.
 18 |     if (head == NULL)
 19 |     {
 20 |         new = malloc(sizeof(Node));
 21 |         if (new == NULL)
 22 |             return NULL;
 23 |         
 24 |         new->data = data;
 25 |         head = new;
 26 |         new->next = NULL;
 27 |     } else {
 28 |         new = malloc(sizeof(Node));
 29 |         if (new == NULL)
 30 |             return NULL;
 31 |         
 32 |         new->data = data;
 33 |         new->next = head;
 34 |         head = new;
 35 |     }
 36 | 
 37 |     return new;
 38 | }
 39 | 
 40 | // remove a node from the list
 41 | int removeNode(int data)
 42 | {
 43 |     Node *current = head;
 44 |     Node *prev = head;
 45 |     while (current != NULL)
 46 |     {
 47 |         if (current->data == data)
 48 |         {
 49 |             // if current node is the list head
 50 |             if (current == head)
 51 |             {
 52 |                 head = current->next;
 53 |             } else {
 54 |                 prev->next = current->next;
 55 |                 free(current);
 56 |                 current = NULL;
 57 |             }
 58 | 
 59 |             return 1;
 60 |         }
 61 |         prev = current;
 62 |         current = current->next;
 63 |     }
 64 | 
 65 |     return 0;
 66 | }
 67 | 
 68 | // insert a node into a position in the list
 69 | Node *insertNode(int data, int position)
 70 | {
 71 |     Node *current = head;
 72 |     while (current != NULL && position != 0)
 73 |     {
 74 |         position--;
 75 |     }
 76 | 
 77 |     if (position != 0)
 78 |     {
 79 |         printf("Requested position too far into list\n");
 80 |         return NULL;
 81 |     }
 82 | 
 83 |     Node *new = malloc(sizeof(Node));
 84 |     if (new == NULL)
 85 |         return NULL;
 86 | 
 87 |     new->data = data;
 88 |     new->next = current->next;
 89 |     current->next = new;
 90 | 
 91 |     return new;
 92 | }
 93 | 
 94 | // print operation
 95 | void printList()
 96 | {
 97 |     Node *current = head;
 98 |     while (current != NULL)
 99 |     {
100 |         printf("%d->", current->data);
101 |         current = current->next;
102 |     }
103 | 
104 |     printf("\n");
105 |     return;
106 | }
107 | 
108 | void printMenu()
109 | {
110 |     printf("You have the following options:\n");
111 |     printf("\t1. Add a node to the list.\n");
112 |     printf("\t2. Remove a node from the list.\n");
113 |     printf("\t3. Insert a node to the list.\n");
114 |     printf("\t4. Print your list\n");
115 |     printf("\t5. Quit.\n");
116 |     return;
117 | }
118 | 
119 | 
120 | int main(int argc, char **argv)
121 | {
122 |     int option = -1;
123 |     int arg1 = 0;
124 |     int arg2 = 0;
125 |     while (option != 5)
126 |     {
127 |         printMenu();
128 |         int num_received = scanf("%d", &option);
129 |         if (num_received == 1 && option > 0 && option <= 5)
130 |         {
131 |             switch(option)
132 |             {
133 |                 case 1:
134 |                     // add operation
135 |                     printf("What data should I insert?:\n");
136 |                     scanf("%d", &arg1);
137 |                     Node *new = addNode(arg1);
138 |                     break;
139 |                 case 2:
140 |                     // remove operation
141 |                     printf("What data should I remove?:\n");
142 |                     scanf("%d", &arg1);
143 |                     int success = removeNode(arg1);
144 |                     if (!success)
145 |                         printf("Element not found\n");
146 | 
147 |                     break;
148 |                 case 3:
149 |                     // insert operation
150 |                     // remove operation
151 |                     printf("What data should I insert?:\n");
152 |                     scanf("%d", &arg1);
153 |                     printf("What position?:\n");
154 |                     scanf("%d", &arg2);
155 |                     new = insertNode(arg1, arg2);
156 |                     if (new == NULL)
157 |                         printf("Failed to insert into list\n");
158 |                     break;
159 |                 case 4:
160 |                     // print the list
161 |                     printList();
162 |                     break;
163 |                 case 5:
164 |                     break;
165 |             }
166 |         }
167 |     }
168 |     
169 | 
170 |     return 0;
171 | }


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