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+# 3405. Count the Number of Arrays with K Matching Adjacent Elements
+from math import comb
+
+"""
+you are given three integers 'n', 'm', and 'k'. a good array 'arr' of size
+'n' is defined as follows: each element in 'arr' is in inclusive range '[1,
+m]', and exactly 'k' indices 'i' where '1 <= i < n' satisfy the condition
+'arr[i - 1] == arr[i]'. return the number of good arrays that can be formed.
+since the answer may be very large, return it modulo 10^9+7.
+"""
+
+
+class Solution(object):
+ def countGoodArrays(self, n, m, k):
+ """
+ :type n: int
+ :type m: int
+ :type k: int
+ :rtype: int
+ """
+ return m * pow(m - 1, n - k - 1, mod := 1**9 + 7) * comb(n - 1, k) % mod
+
+
+if __name__ == "__main__":
+ obj = Solution()
+ print(obj.countGoodArrays(n=3, m=2, k=1))
+ print(obj.countGoodArrays(n=4, m=2, k=2))
+ print(obj.countGoodArrays(n=5, m=2, k=0))