BUPT-homework/semester2/pset1/4-Joseph.c

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

typedef struct Node {
  // Clockwise order
  struct Node *next;
  // Anti clockwise order
  struct Node *prev;
  // Starts from 1, clockwise
  int id;
} Node;

Node *constructRing(int len);
Node *appendNode(Node *head, int id);
Node *deleteNode(Node *head, int direction);
Node *iterateNode(Node *head, int direction,
                  int count); // 1: clockwise, 0: anti clockwise

int main(void) {
  int n, m, k;
  scanf("%d%d%d", &n, &m, &k);

  Node *head = constructRing(n);

  int count = 0;
  for (int i = 0; i < n; i++) {

    // determine the count
    if (i % 2 == 0) { // Anti clockwise
      count = m;
    } else {
      count = k;
    }

    head = iterateNode(head, i % 2, count);

    printf("%d ", head->id);
    head = deleteNode(head, i % 2);
  }

  return 0;
}

Node *constructRing(int len) {
  // Construct the first node
  Node *head = malloc(sizeof(Node));
  head->id = 1;
  head->prev = NULL;
  head->next = NULL;

  Node *ptr = head;

  for (int i = 2; i <= len; i++) {
    ptr = appendNode(ptr, i);
  }
  ptr->next = head;
	head->prev = ptr;

  return head;
}

Node *appendNode(Node *head, int id) {
  Node *new = malloc(sizeof(Node));
  new->id = id;
  new->prev = head;
  new->next = NULL; // Can be deleted

  head->next = new;
  return new;
}

Node *deleteNode(Node *head, int direction) {
  Node *prev = head->prev;
  Node *next = head->next;

	if (head == next) {// Single element in the ring
		free(head);
		return NULL;
	}

  prev->next = next;
  next->prev = prev;
  free(head);

  if (direction == 1)
    return next;
  else
    return prev;
}

Node *iterateNode(Node *head, int direction,
                  int count) { // 1: clockwise, 0: anti clockwise
  Node *ptr = head;
  for (int i = 1; i < count; i++) { // starts from 1
    if (direction == 1)
      ptr = ptr->next;
    else
      ptr = ptr->prev;
  }

  return ptr;
}