给定一个单向链表,编写函数交换相邻 两个元素
输入: 1 -> 2 -> 3 -> 4 -> 5 -> 6 -> 7
输出: 2 -> 1 -> 4 -> 3 -> 6 -> 5 -> 7
输入: 1 -> 2 -> 3 -> 4 -> 5 -> 6
输出: 2 -> 1 -> 4 -> 3 -> 6 -> 5
通过观察发现:当输入的与元素个数是单数的时候，最后一位不参与交换。
方法1（迭代)
从头节点开始遍历列表，遍历过程中使用每个节点的下一个节点和当前节点的数据进行交换。
时间复杂度：O(n)
实现过程：
c语言
/* C Program to pairwise swap elements in a given linked list */
#include <stdio.h>
#include <stdlib.h>
/* A linked list node*/
struct Node {
int data;
struct Node* next;
};
/* Function to swap two integers at addresses a and b */
void swap(int *a, int *b);
/* Function to pairwise swap elements of a linked list */
void pairWiseSwap(struct Node* head)
{
struct Node* temp = head;
/* Traverse further only if there are at-least two nodes left */
while( temp != NULL && temp->next != NULL)
{
/* Swap data of node with its next node‘s data */
swap(&temp->data, &temp->next->data);
/* Move temp by 2 for the next pair*/
temp = temp->next->next;
}
}
/* Utility functions */
/* function to swap two integers */
void swap(int *a, int *b)
{
int temp;
temp = *a;
*a = *b;
*b = temp;
}
/* Funtion to add a node at the beginning of Linked List*/
void push(struct Node** head_ref, int new_data)
{
/* allocate node */
struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
/* put in the data */
new_node->data = new_data;
/* link the old list off the new node */
new_node->next = (*head_ref);
/* move the head to point to the new node */
(*head_ref) = new_node;
}
/* function to print nodes in a given linked list */
void printList(struct Node* node)
{
while( node != NULL )
{
printf("%d ", node->data);
node = node->next;
}
printf("\n");
}
/* driver program to test above function */
int main() {
struct Node* start = NULL;
/*
the constructed linked list is:
1 -> 2 -> 3 -> 4 -> 5
*/
push(&start ,5);
push(&start, 4);
push(&start, 3);
push(&start, 2);
push(&start, 1) ;
printf("Linked list before calling pairwise swap function\n");
printList(start);
pairWiseSwap(start);
printf("Linked list after calling pairwise swap function\n");
printList(start);
return 0;
}
结果
java代码：
// Java program to pairwise swap elements of a linked list
class LinkedList {
Node head; // head of list
/* Linked list Node*/
class Node {
int data;
Node next;
Node(int d)
{
data = d;
next = null;
}
}
void pairWiseSwap()
{
Node temp = head;
/* Traverse only till there are atleast 2 nodes left */
while (temp != null && temp.next != null) {
/* Swap the data */
int k = temp.data;
temp.data = temp.next.data;
temp.next.data = k;
temp = temp.next.next;
}
}
/* Utility functions */
/* Inserts a new Node at front of the list. */
public void push(int new_data)
{
/* 1 & 2: Allocate the Node &
Put in the data*/
Node new_node = new Node(new_data);
/* 3. Make next of new Node as head */
new_node.next = head;
/* 4. Move the head to point to new Node */
head = new_node;
}
/* Function to print linked list */
void printList()
{
Node temp = head;
while (temp != null) {
System.out.print(temp.data + " ");
temp = temp.next;
}
System.out.println();
}
/* Driver program to test above functions */
public static void main(String args[])
{
LinkedList llist = new LinkedList();
/* Created Linked List 1->2->3->4->5 */
llist.push(5);
llist.push(4);
llist.push(3);
llist.push(2);
llist.push(1);
System.out.println("Linked List before calling pairWiseSwap() ");
llist.printList();
llist.pairWiseSwap();
System.out.println("Linked List after calling pairWiseSwap() ");
llist.printList();
}
}
/* This code is contributed by Rajat Mishra */
c#代码
// C# program to pairwise swap elements of a linked list
using System;
class LinkedList {
Node head; // head of list
/* Linked list Node*/
public class Node {
public int data;
public Node next;
public Node(int d)
{
data = d;
next = null;
}
}
void pairWiseSwap()
{
Node temp = head;
/* Traverse only till there are atleast 2 nodes left */
while (temp != null && temp.next != null) {
/* Swap the data */
int k = temp.data;
temp.data = temp.next.data;
temp.next.data = k;
temp = temp.next.next;
}
}
/* Utility functions */
/* Inserts a new Node at front of the list. */
public void push(int new_data)
{
/* 1 & 2: Allocate the Node &
Put in the data*/
Node new_node = new Node(new_data);
/* 3. Make next of new Node as head */
new_node.next = head;
/* 4. Move the head to point to new Node */
head = new_node;
}
/* Function to print linked list */
void printList()
{
Node temp = head;
while (temp != null) {
Console.Write(temp.data + " ");
temp = temp.next;
}
Console.WriteLine();
}
/* Driver program to test above functions */
public static void Main(String[] args)
{
LinkedList llist = new LinkedList();
/* Created Linked List 1->2->3->4->5 */
llist.push(5);
llist.push(4);
llist.push(3);
llist.push(2);
llist.push(1);
Console.WriteLine("Linked List before calling pairWiseSwap() ");
llist.printList();
llist.pairWiseSwap();
Console.WriteLine("Linked List after calling pairWiseSwap() ");
llist.printList();
}
}
// This code is contributed by Arnab Kundu
方法2（递归）
如果链表中含有两个以上节点,先交换前两个节点,然后递归调用剩下的节点
时间复杂度:O(n)
算法主要部分代码
/* Recursive function to pairwise swap elements
of a linked list */
void pairWiseSwap(struct node* head)
{
/* There must be at-least two nodes in the list */
if (head != NULL && head->next != NULL) {
/* Swap the node‘s data with data of next node */
swap(&head->data, &head->next->data);
/* Call pairWiseSwap() for rest of the list */
pairWiseSwap(head->next->next);
}
}
以上代码只是交换数据域部分的指针，如果一个节点含有很多字段，将会产生频繁的交换动作。
文章来源：https://www.geeksforgeeks.org/pairwise-swap-elements-of-a-given-linked-list/
原文地址：https://www.cnblogs.com/passedbylove/p/11439473.html
时间： 2024-10-25 20:02:50