题解 | #牛牛的链表交换#

#include <math.h>
#include<stdio.h>
#include <stdlib.h>

typedef struct node {
    int num;
    struct node* next;
} Node ;

Node* createnode(int num) {
    Node* ptr = (Node*)malloc(sizeof(Node));
    if (ptr == NULL) {
        printf("malloc error!\n");
        exit(0);
    }
    ptr->num = num;
    ptr->next = NULL;
    return ptr;
}

void add_node(Node* head,int num)
{
    Node* q=(Node*)malloc(sizeof(Node));
    q->num=num;
    q->next=NULL;
    Node *p=head;
    while(p->next!=NULL)
    {
        p=p->next;
    }
    p->next=q;
}

void swap_node(Node* head, int n) {
    Node* p = head;
    while (n--)
        p = p->next;
    int num1 = p->num, num2 = p->next->num;
    p->num = num2;
    p->next->num = num1;
}

void Printlist(Node* head) {
    Node* p = head;
    while (p) {
        printf("%d ", p->num);
        p = p->next;
    }
}

int main() {
    int n;
    scanf("%d", &n);
    int* a = (int*)malloc(n * sizeof(int));
    if (a == NULL) {
        printf("malloc error!\n");
        exit(0);
    }
    for (int i = 0; i < n; i++)
        scanf("%d", &a[i]);
    Node* head=createnode(a[0]);
    for (int i = 1; i < n; i++)
        add_node(head, a[i]);
    swap_node(head, 0);
    swap_node(head, n - 2);
    Printlist(head);
    Node* temp;
    while (head != NULL) {
        temp = head;
        head = head->next;
        free(temp);
    }

    free(a);
    return 0;
}