单链表中交换元素

前言

链表中的交换元素，不同于数组。链表中的操作主要是针对结构中的next

步骤

void Exchange(Position BeforeP)//我这里传入表头
{
    //为交换P和AfterP
    Position P, AfterP;
    //定义一下P，和AfterP
    P = BeforeP->next;
    AfterP = P->next;

    //交换是针对3个结构中的next。
    //先想象已经把两个结构交换了，再考虑next要怎么指向
    P->next = AfterP->next;
    BeforeP->next = AfterP;
    AfterP->next = P;
    
}

示例

单链表

#include<stdio.h>
#include<stdlib.h>
typedef struct Node * PtrToNode;
typedef PtrToNode List;
typedef PtrToNode Position;
void Exchange (Position BeforeP);
void PrintList(List L);
struct Node 
{
    int e;
    PtrToNode next;
};

int main()
{
    List L = NULL;
    Position prev, current; 
    int n = 0;
    while (n < 4)
    {
        current = (PtrToNode)malloc(sizeof(struct Node));
        if(L == NULL)
            L = current;
        else
            prev->next = current;
        current->next = NULL;
        current->e = n;
        prev = current;

        n++;
    }
    PrintList(L);
    Exchange(L);
    PrintList(L);

    return 0;
}

void Exchange(Position BeforeP)//我这里传入表头
{
    //为交换P和AfterP
    Position P, AfterP;
    //定义一下P，和AfterP
    P = BeforeP->next;
    AfterP = P->next;
    //交换是针对3个结构中的next。
    //先想象已经把两个结构交换了，再考虑next要怎么指向
    P->next = AfterP->next;
    BeforeP->next = AfterP;
    AfterP->next = P;
    
}

void PrintList(List L)
{
    while (L != NULL)
    {
        printf("%d ", L->e);
        L = L->next;
    }
    printf("\n");
}