DS-005 31 数据结构：双向链表及代码实现

Code Implementation of Double link list

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1 Construction of a double link list

1.1 Construct the node

typedef struct line{
    struct line * prior; // Point to the precursor
    int data;
    struct line * next; // Point to the subsequence
}line;

1.2 Initialization

line* initLine(line * head){
	head=(line*)malloc(sizeof(line));	// Create the first node
	head->prior=NULL;
	head->next=NULL;
	head->data=1;
	line * list=head;
	for (int i=2;i<=5;i++){				// Initialize and create a node
		line * body=(line*)malloc(sizeof(line));
		body->prior=NULL;
		body->next=NULL;
		body->data=i;
		
		list->next=body;				// Subsequence points to the new node
		body->prior=list;				// New node points to the precursor
		list=list->next;
	}
	return head;
}

1.3 Display the list

void display(line * head){
    line * temp=head;
    while (temp) {
        if (temp->next==NULL) {			// If no 'next', means the node is the last one
            printf("%d\n",temp->data);
        }else{
            printf("%d <-> ",temp->data);
        }
        temp=temp->next;
    }
}
int main() {
    line * head=NULL;		// Create a head pointer 
    head=initLine(head);	// Create the list
    display(head);
    printf("The 4th's direct precursor in the list is：%d",head->next->next->next->prior->data);
    return 0;
}

Output:

2 Basic operations of double link list

2.1 Insert elements

line * insertLine(line * head,int data,int add){
    line * temp=(line*)malloc(sizeof(line));
    temp->data=data;
    temp->prior=NULL;
    temp->next=NULL;
    if (add==1) {				// Special condition: Insert to the head	
        temp->next=head;
        head->prior=temp;
        head=temp;
    }else{
        line * body=head;
        for (int i=1; i<add-1; i++) {		// Find the last node of the inserted place
            body=body->next;
        }
        if (body->next==NULL) {				// If true, the place is on the tail
            body->next=temp;
            temp->prior=body;
        }else{
            body->next->prior=temp;
            temp->next=body->next;
            body->next=temp;
            temp->prior=body;
        }
    }
    return head;
}

2.2 Delete elements

line * delLine(line * head,int data){
    line * temp=head;
    while (temp) {		// Traversal
        if (temp->data==data) {
            temp->prior->next=temp->next;
            temp->next->prior=temp->prior;
            free(temp);
            return head;
        }
        temp=temp->next;
    }
    printf("No such element");
    return head;
}

2.3 Find the element

int selectElem(line * head,int elem){
    line * t=head;		// Initialized as head pointer
    int i=1;
    while (t) {
        if (t->data==elem) {
            return i;
        }
        i++;
        t=t->next;
    }
    return -1;			// Failed to find the target
}

2.4 Alter the element

line *amendElem(line * p,int add,int newElem){
    line * temp=p;
    for (int i=1; i<add; i++) {		// Traversed to the deleted node
        temp=temp->next;
    }
    temp->data=newElem;
    return p;
}

2.5 Check the code

void display(line * head){
    line * temp=head;
    while (temp) {
        if (temp->next==NULL) {
            printf("%d\n",temp->data);
        }else{
            printf("%d->",temp->data);
        }
        temp=temp->next;
    }
}
int main() {
    line * head=NULL;
    head=initLine(head);			// Create the list
    display(head);
	head=insertLine(head, 7, 3);	// Insert element 7 at the position 3
    display(head);
    head=delLine(head, 2);			// Delete element 2
    display(head);
    printf("Element 3's position：%d\n",selectElem(head,3));
    head = amendElem(head,3,6);		// Change the 3rd node to store number 6
    display(head);
    return 0;
}

Output: