单链表逆置

西安电子科技大学数据结构与算法上机实验——单链表逆置

先通过一次遍历所有结点，判断其个数值，进而得到中间结点的位置，定义两个工作指针一个从前向后开始移动，另一个从最后像前面逆向移动，移动的过程中进行循环交换中间结点对称两侧的节点数值，不改变原结点的连接情况

#include<malloc.h>
#include<stdio.h>

# define LEN sizeof(struct linklist)

struct linklist {
    int num;
    struct linklist *next;
};

struct linklist *create();

void print(struct linklist *);

void invert(struct linklist *);

int main(void) {
    struct linklist *head;
    printf("***************请创建链表*****************\n");
    head = create();
    printf("***************输出原链表*****************\n");
    print(head);
    invert(head);//调用单链表逆置的函数
    printf("************输出逆置后的链表**************\n");
    print(head);
    return 0;
}

struct linklist *create() {
    struct linklist *p, *q, *head = NULL;
    p = q = (struct linklist *) malloc(LEN);
    scanf("%d", &p->num);
    while (p->num != 0) {
        if (head == NULL) {
            head = p;
        } else {
            q->next = p;
        }
        q = p;
        p = (struct linklist *) malloc(LEN);
        scanf("%d", &p->num);
    }
    q->next = 0;
    free(p);
    return head;
}

void print(struct linklist *const head) {
    struct linklist *p = head;
    do {
        printf("%d ", p->num);
        p = p->next;
    } while (p != NULL);
    printf("\n");
}

void invert(struct linklist *const head) {
    int i, j, t, m, n = 0;
    struct linklist *p = head, *q;
    while (p != NULL) {
        p = p->next;
        n++;
    }
    p = head;
    m = n / 2;
    for (i = 0; i < m; i++) {
        q = head;
        for (j = 0; j < n - 1; j++) {
            q = q->next;
        }
        t = p->num;
        p->num = q->num;
        q->num = t;
        p = p->next;
        n--;
    }
}