两两交换链表中的节点C语言流程图

以下是交换链表中相邻的两个节点的C语言代码及流程图：

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

// 定义链表节点
typedef struct ListNode {
    int val;
    struct ListNode *next;
} ListNode;

// 交换相邻的两个节点
ListNode* swapPairs(ListNode* head) {
    ListNode *dummy = (ListNode *)malloc(sizeof(ListNode));
    dummy->next = head;
    ListNode *cur = dummy;

    while (cur->next && cur->next->next) {
        ListNode *first = cur->next;
        ListNode *second = cur->next->next;
        first->next = second->next;
        cur->next = second;
        cur->next->next = first;
        cur = cur->next->next;
    }

    return dummy->next;
}

// 创建链表
ListNode* createList(int arr[], int n) {
    ListNode *dummy = (ListNode *)malloc(sizeof(ListNode));
    ListNode *cur = dummy;

    for (int i = 0; i < n; i++) {
        ListNode *node = (ListNode *)malloc(sizeof(ListNode));
        node->val = arr[i];
        cur->next = node;
        cur = cur->next;
    }

    cur->next = NULL;

    return dummy->next;
}

// 打印链表
void printList(ListNode *head) {
    while (head) {
        printf("%d ", head->val);
        head = head->next;
    }
    printf("\n");
}

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    int n = sizeof(arr) / sizeof(int);

    ListNode *head = createList(arr, n);
    printf("Original List: ");
    printList(head);

    head = swapPairs(head);
    printf("Swapped List: ");
    printList(head);

    return 0;
}

流程图如下：

graph LR
    dummy((dummy)) --> cur((cur))
    cur --> |next| node1((1))
    node1 --> |next| node2((2))
    node2 --> |next| node3((3))
    node3 --> |next| node4((4))
    node4 --> |next| node5((5))
    node5 --> |next| NULL((NULL))
    cur --> |next| first((1))
    first --> |next| second((2))
    second --> |next| node3
    cur --> |next| second
    second --> |next| first
    first --> |next| node4
    cur --> |next| first
    first --> |next| second
    second --> |next| node5
    first --> |next| node5
    second --> |next| NULL
    first --> |next| NULL
    dummy --> |next| second
    second --> |next| first
    first --> |next| node2
    second --> |next| node1
    first --> |next| node3
    second --> |next| node4
    first --> |next| node5
    second --> |next| NULL
    node2 --> |next| node1
    node1 --> |next| node4
    node4 --> |next| node3
    node3 --> |next| node5
    node5 --> |next| NULL

其中，dummy 表示虚拟头节点，cur 表示当前节点，first 和 second 分别表示交换的两个节点。节点之间的箭头表示它们之间的关系，如 `node1 --> |next| node2` 表示 node1 指向 node2。