2020牛客暑期多校训练营（第六场）E题

链接：https://ac.nowcoder.com/acm/contest/5671/E
来源：牛客网

#pragma warning (disable:4996)
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define inf 0X3f3f3f3f
using namespace std;
typedef long long ll;
typedef unsigned long long ull;

const int maxn = 5000 + 20;
vector<int> p;
vector<int> a;
bool vis[maxn];
int n, k;

bool exist()
{
     
 for (int len = 2; len < n; len++)
 {
     
  bool flag = 0;
  for (int i = 0; i + len <= n; i++)
  {
     
   int sum = a[i + len] - a[i];
   if (sum % n == k)
   {
     
    flag = 1;
    break;
   }
  }
  if (!flag)
   return 0;
 }
 return 1;
}

bool fun(int index)
{
     
 int res = 0;
 if (index > n)
 {
     
  if (exist())
  {
     
   //reverse(p.begin(), p.end());
   while (p.size())
   {
     
    if (p.size() == 1)
     printf("%d", p.back());
    else
     printf("%d ", p.back());
    p.pop_back();
   }
   printf("\n");
   return 1;
  }
 }
 for (int i = 1; i <= n; i++)
  if (vis[i] == 0)
  {
     
   p.push_back(i);
   a.push_back(a[a.size() - 1] + i);
   vis[i] = 1;
   res = fun(index + 1);
   if (res)
    break;
   p.pop_back();
   a.pop_back();
   vis[i] = 0;
  }
 return res;
}

int main()
{
     
 scanf("%d%d", &n, &k);
 int sum = 0;
 for (int i = 1; i <= n; i++)
  sum += i;
 if (sum % n != k)
 {
     
  printf("-1\n");
  return 0;
 }
 //a.push_back(0);
 //if (!fun(1))
 printf("%d ", n);
 if (k != 0)
  printf("%d ", k);
 for (int i = 1; i < n / 2; i++)
  printf("%d %d ", i, n - i);
 if (n / 2 != k)
  printf("%d %d ", n / 2, n / 2 + 1);
 printf("\n");
 return 0;
}