add Combination.py

Author: ryusuke920

Math/Combination.py

@@ -0,0 +1,31 @@
+class Combination:
+    def __init__(self, N: int, MOD: int) -> None:
+        self.N = N + 100
+        self.MOD = MOD
+        self.fac = [0]*(self.N + 1)
+        self.fac_inv = [0]*(self.N + 1)
+        self.fac[0] = 1
+        self.fac_inv[0] = 1
+
+        for i in range(1, self.N + 1):
+            self.fac[i] = self.fac[i - 1] * i
+            self.fac[i] %= self.MOD
+        
+        for i in range(1, self.N + 1):
+            self.fac_inv[i] = pow(self.fac[i], self.MOD - 2, self.MOD)
+    
+    def nCr(self, N: int, R: int) -> int:
+        return self.fac[N]*self.fac_inv[R]*self.fac_inv[N - R] % self.MOD
+
+    def nPr(self, N: int, R: int) -> int:
+        return self.nCr(N, R)*self.fac[R] % self.MOD
+
+
+def main() -> None:
+    N = 10**5
+    mod = 998244353
+    Com = Combination(N, mod)
+
+
+if __name__ == "__main__":
+    main()