Exemple #1
0
        public static void Main(string[] args)
        {
            int N = ri;
            int K = ri;

            int[] A = ria;

            Mint ans = 0;

            Sort(A);

            if (K == 1)
            {
                Console.WriteLine(0);
                return;
            }

            Mint[] maxCounts = new Mint[N];
            Mint[] minCounts = new Mint[N];
            for (int i = 0; i < N; i++)
            {
                // A[i]が最大値になる回数
                maxCounts[i] = Combination.nCk(i, K - 1);

                // A[i]が最小値になる回数
                minCounts[i] = Combination.nCk(N - i - 1, K - 1);
            }

            for (int i = 0; i < N; i++)
            {
                ans += A[i] * maxCounts[i];
                ans -= A[i] * minCounts[i];
            }

            Console.WriteLine(ans);
        }
Exemple #2
0
                                                                                                                  public static Mint nCkForBigNSmallK(long n, long k)
                                                                                                                  {
                                                                                                                      Mint x = 1; Mint y = 1; for (int i = 0; i < k; i++)

                                                                                                                      {
                                                                                                                          x *= n - i; y *= i + 1;
                                                                                                                      }
                                                                                                                      return(x / y);
                                                                                                                  }
Exemple #3
0
 } } public class Combination { static long SIZE = (long)1e7 + 1; static Mint[] mFactorial, mFactrialInverse, mInverse; private static void Init()
                                {
                                    mFactorial = new Mint[SIZE]; mFactrialInverse = new Mint[SIZE]; mInverse = new Mint[SIZE]; mFactorial[0] = mFactorial[1] = 1; mFactrialInverse[0] = mFactrialInverse[1] = 1; mInverse[1] = 1; for (int i = 2; i < SIZE; i++)
                                    {
                                        mFactorial[i] = mFactorial[i - 1] * i; mInverse[i] = -1 * mInverse[Mint.MOD % i] * (Mint.MOD / i); mFactrialInverse[i] = mFactrialInverse[i - 1] * mInverse[i];
                                    }
                                }