翻转链表.

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

#define COLOR(a,b) "\033[" #b "m" a "\033[0m"
#define GREEN(a) COLOR(a,32)
typedef struct Node {
  int data;
  struct Node* next;
} Node;

typedef struct List {
  Node head;//定义虚拟头节点
  int length;
}List;

Node* getNewNode(int);
List* init_list();
int insert(List*, int, int);
int erase(List*, int);
void clear_node(Node*);
void clear_List(List*);
void output(List*);

Node* getNewNode(int val) {
  Node* node = (Node*)malloc(sizeof(Node));
  node->data = val;
  node->next = NULL;
  return node;
}

List* init_list() {
  List* list = (List*)malloc(sizeof(List));
  list->head.next = NULL;
  list->length = 0;
  return list;
}

int insert(List* l, int ind, int val) {
  if (l == NULL) return 0;
  if(ind < 0 || ind > l->length) return 0;
  Node* p = &(l->head), * node = getNewNode(val);
  while (ind--) p = p->next;
  node->next = p->next;
  p->next = node;
  l->length += 1;
  return 1;
}

int erase(List* l, int ind) {
  if (l == NULL) return 0;
  if (ind < 0 || ind >= l->length) return 0;
  Node* p = &(l->head), * q;
  while (ind--) p = p->next;
  q = p->next;
  p->next = q->next;
  clear_node(q);
  l->length -= 1;
  return 1;
}


void clear_node(Node* node) {
  if (node == NULL) return;
  free(node);
  return;
}

void clear_list(List* list) {
  if (list == NULL) return;
  Node* p = list->head.next, * q;
  while (p) {
    q = p->next;
    free(p);
    p = q;
  }
  free(list);
  return;
}

void output(List* l) {
  if (l == NULL) return;
  printf("list(%d):", l->length);
  for (Node* p = l->head.next; p; p = p->next) {
    printf("%d->", p->data);
  }
  printf("NULL\n");
  return;
}

void reverse(List* l) {
  if (l == NULL)  return;
  Node* p = l->head.next, * q;
  l->head.next = NULL;
  while (p) {
    q = p->next;
    p->next = l->head.next;
    l->head.next = p;
    p = q;
  }
  return ;
}
int main() {
  srand(time(0));
  #define MAX_OP 20
  List* l = init_list();
  for (int i = 0; i < MAX_OP; i++) {
    int val = rand() % 100;
    int ind = rand() % (l->length + 3) - 1;
    int op = rand() % 4;
    switch (op) {
      case 0:
      case 1: {
        printf(GREEN("reverse the list!\n"));
        reverse(l);
      }break;
      case 2: {
        printf("insert %d at %d to List = %d\n", val, ind, insert(l, ind, val));
      }break;
      case 3: {
        printf("erase a item at %d from List = %d\n", ind, erase(l, ind));
      }break;
    }
    output(l);
    printf("\n");
  }
  return 0;
}