First commit

lib/arithmetics.py

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+# Arithmetics functions implementaton
+
+def modpow(a: int, b: int, m: int) -> int:
+    result = 1 
+    while b > 0:
+        if (b & 1) > 0:
+            result = (result * a) % m
+        b = b >> 1 
+        a = (a * a) % m 
+    return result
+
+def gcd(a: int, b: int) -> int:
+    if b == 0:
+        return a
+    return gcd(b, a % b)
+
+def mod_inverse(A: int, M: int) -> int:
+    m0 = M
+    y = 0
+    x = 1
+    if (M == 1):
+        return 0
+    while (A > 1):
+        # q is quotient
+        q = A // M
+        t = M
+        # m is remainder now, process
+        # same as Euclid's algo
+        M = A % M
+        A = t
+        t = y
+        # Update x and y
+        y = x - q * y
+        x = t
+    # Make x positive
+    if (x < 0):
+        x = x + m0
+    return x
+