DataStructure-single linked list operation

Singly Linked List Operations

topic

Singly linked list construction, insertion, deletion, modification, search (generally not used, simple traversal)

Example 1

A and B are two single-linked lists (leading nodes), in which the elements are in ascending order. Design an algorithm to merge A and B into one non-decreasing linked list C by elements. C is composed of nodes in A and B.

analyze:

A, B singly linked list elements are incremented, just select a smaller one from the start nodes of A and B to insert at the end of C,

For the remaining elements in A and B, just connect A or B to the end of C.

enter:

1 3 5 7 -1
2 4 6 8 -1

output:

1 2 3 4 5 6 7 8 9

Head interpolation - creating a linked list

//创建链表1.头插法
void CreateListHead(List C){
	LNode* s,* r;
	C = (LNode*)malloc(sizeof(LNode));
	C->next = NULL;
	r = C;
	int x = 0;
	while (scanf_s("%d", &x) && x > 0) {
		s = (LNode*)malloc(sizeof(LNode));//s指向新申请的结点
		s->data=x;
        /*下边两句是头插法的灵魂*/
		r->next = s;//用r来接受新的结点
        //为什么不用L->next=s;ans：如果这样操作，头结点就会丢失,最終头结点会指向最后一个节点
		r = r->next;//r指向终端结点，以便于接纳下一个新到来的LNode
	}
	r->next = NULL;
}

Tail insertion method - create a linked list

//创建链表2.尾插法
void CreateListBack(LNode *&C) {
	LNode* s;
	C = (LNode*)malloc(sizeof(LNode));
	C->next = NULL;
	int x;
	while (scanf_s("%d", &x) && x > 0) {
		s = (LNode*)malloc(sizeof(LNode));
		s->data = x;
		s->next = C->next;//s所指新结点的指针域next指向C的开始结点
		C->next = s;//头结点指针域next指向s结点，0使得s成为新的开始结点

	}
}

Connect double-linked list by head interpolation

//头插法
void mergeHead(LNode* A, LNode* B, LNode*& C) {
	LNode* p = A->next;
	LNode* q = B->next;
	LNode* r;//r始终指向C的终端结点
	C = A;
	C->next = NULL;
	free(B);
	r = C;
	while (p != NULL && q != NULL) {
		if (p->data <= q->data) {
			r->next = p; p = p->next;
			r = r->next;
		}
		else {
			r->next = q; q = q->next;
			r = r->next;
		}
	}
	if (p != NULL) r->next = p;
	if (q != NULL) r->next = q;
}

Tail insertion double linked list join

Extension: tail insertion double linked list connection

void mergeBack(LNode* A, LNode* B, LNode* &C) {
	LNode* p = A->next;
	LNode* q = B->next;
	LNode* s;
	C = A;
	C->next = NULL;
	free(B);
	while (p != NULL && q != NULL) {
		if (p->data <= q->data) {
			s = p; p = p->next;
			s->next = C->next;
			C->next = s;
		}
		else {
			s = q; q = q->next;
			s->next = C->next;
			C->next = s;
		}
	}
	while (p != NULL) {
		s = p;
		p = p->next;
		s->next = C->next;
		C->next = s;
	}
	while (q != NULL) {
		s = q;
		q = q->next;
		s->next = C->next;
		C->next = s;
	}
}

complete program

#include<iostream>
using namespace std;
typedef struct LNode {
	int data;
	struct LNode* next;
}LNode, *List ;
void CreateListHead(LNode* &L) {
	L = (LNode*)malloc(sizeof(LNode));
	L->next = NULL;
	LNode* r,*s;
	r = L;
	int x = 0;
	while (scanf_s("%d", &x) && x > 0) {
		s = (LNode*)malloc(sizeof(LNode));
		s->data = x;
		r->next = s;
		r = r->next;
	}
	r->next = NULL;//输入元素已全部装入链表，L的终端终点指针域置为NULL，L建立完毕
	//如果缺少这一步，会导致链表遍历指针域未初始化
}
void mergeHead(LNode* A, LNode* B, LNode*& C) {
	LNode* p = A->next;
	LNode* q = B->next;
	LNode* r;//r始终指向C的终端结点
	C = A;
	C->next = NULL;
	free(B);
	r = C;
	while (p != NULL && q != NULL) {
		if (p->data <= q->data) {
			r->next = p; p = p->next;
			r = r->next;
		}
		else {
			r->next = q; q = q->next;
			r = r->next;
		}
	}
	if (p != NULL) r->next = p;
	if (q != NULL) r->next = q;
}
int main() {
	
	List L1, L2;
	
	CreateListHead(L1);
	CreateListHead(L2);
	List L3;
	mergeHead(L1,L2,L3);
	while (L3->next != NULL) {
		cout << L3->next->data << " ";
		L3 = L3->next;                     
	}

	return 0;
}