Complex Structures

Complex Structures • Nested Structures • Self referential structures • A structure may have • Data variables • Internal structures/unions • Pointer links • Function pointers struct course { int course_num; struct student[20]; struct course *next; int (*average)(int []); };

Dynamic Structures • Link Lists • A type of data structure that have its elements linked together • Generic on-demand dynamic structure • Easy manipulation, but may not be efficient • Trees • A type of data structures in which elements are connected in a tree form • Complex data structures • More efficient, use only if the number of elements are large

Link Lists struct slink { int data; struct slink *next; }; • Single Link Lists head struct dlink { int data; struct dlink *next; struct dlink *prev; }; • Double Link lists head Sample Usage: Maintain a dynamic structure of sorted numbers using any of the previous structures Important Functions: void Display_list(struct slink * llist) void Append_Node(struct slink* llist, int data) void Delete_Node(struct slink* llist, int data) int Search_Value(struct slink* llist, int data)

Functions: Single link list //Build a single linked list #include<stdlib.h> #include<stdio.h> struct slink { int data; struct slink *next; }; //Insert is the same way void main() { slink * curr, * head; int i; head = NULL; for(i=1;i<=10;i++) { curr = (slink *)malloc(sizeof(slink)); curr->data = i; curr->next = head; head = curr; } curr = head; } //Display_list(struct slink * llist) void display_list(struct slink *llist) { while(llist->next != NULL) { printf("%d ", llist->data); llist = llist->next; } printf("%d", llist->data); //the last node } //Append_Node(struct slink* llist, int data) void append_node(struct slink *llist, int data) { while(llist->next != NULL) { llist = llist->next; llist->next = (struct slink )malloc(sizeof(struct slink)); llist->next->data = data; llist->next->next = NULL; } }

Functions: Single link list //Delete_Node(struct slink* llist, int data) void delete_node(struct slink *llist, int data) { struct slink *temp; temp = (struct slink *)malloc(sizeof(struct slink)); if(llist->data == data){ /* remove the node */ temp = llist->next; free(llist); llist = temp; } else { //Transverse while(llist->next->data != data) { llist = llist->next; } temp = llist->next->next; free(llist->next); llist->next = temp; } } • //Search_Value(struct slink* llist, int data), return position • int search_value(struct slink *llist, int data) • { • int retval = -1; • int i = 1; • while(llist->next != NULL) • { • if(llist->next->data == data) return i; • else i++; • llist = llist->next; • } • return retval; • }

Functions: Double link list void insert (struct dlink *head, struct dlink *entry) { struct dlink *tmp; for (tmp = head->next; tmp!= head && tmp->data < entry->data; tmp = tmp->next); tmp->prev->next = entry; entry->prev= tmp->prev; tmp->prev = entry; entry->next = tmp; }; void delete (struct dlink *entry) { entry>next->prev = entry->prev; entry>prev->next = entry->next; entry->next = entry->prev = NULL; }; struct dlink * search (struct dlink *head, int val) { struct dlink * tmp; for (tmp = head->next; tmp!= head && tmp->data != val; tmp = tmp->next); return (tmp==head)? NULL : tmp; } int main() { struct dlink num[10] = { … }; struct dlink head={0, NULL, NULL}; for (int i=0; i<10; i++) insert (&head, &num[i]); … return 0; }

Other Link Lists • Hash link lists bin[size] • Other variants: queues and stacks • Queue: a link list grown at one end, shrink at another, i.e. FIFO • Stack: a LIFO link list

Trees – binary trees root struct node { int data; struct node *left; struct node *right; }; left right height leaf

More Trees • Tertiary Trees • Each node has three children • K-ary Trees • Each node has K children • B (Balanced)- Trees • A tree that maintains a balanced height as it grows/shrinks • …

Binary Search Tree void insert (struct node *root, struct node *entry) { /* where to insert is really algorithm dependent. A generic case only: entry is to replace the left node of head */ if (head->left) { entry->left = head->left->left; entry->right = head->left->right; } head->left = entry; }; void delete (struct node *root, struct node *entry) { /* The key is to find a node that has an entry as a child */ }; struct node * search (struct node *root, int val) { if (!root) return NULL; else if (root->data != val) tmp = search(root->left, val); if (!tmp) tmp = search(root->right, val); return tmp; } int main() { struct node num[10] = { … }; struct node root = {0, NULL, NULL}; for (int i=0; i<10; i++) { insert (&root, &num[i]); } … return 0; }

Complex Structures