Added a useful script to compute modular exponentiation.

Author: shivansh-sopho

Mathematical_Algorithms/src/modular_exponentiation.py

@@ -0,0 +1,30 @@
+# Iterative Python3 program 
+# to compute modular power 
+  
+# Iterative Function to calculate 
+# (x^y)%p in O(log y)  
+def power(x, y, p) : 
+    res = 1     # Initialize result 
+  
+    # Update x if it is more 
+    # than or equal to p 
+    x = x % p  
+  
+    while (y > 0) : 
+          
+        # If y is odd, multiply 
+        # x with result 
+        if ((y & 1) == 1) : 
+            res = (res * x) % p 
+  
+        # y must be even now 
+        y = y >> 1      # y = y/2 
+        x = (x * x) % p 
+          
+    return res 
+      
+  
+# Driver Code 
+  
+x = 2; y = 5; p = 13
+print("Power is ", power(x, y, p))