Added documentation for the prime function

Find Prime Numbers/FindPrimes.py

@@ -1,3 +1,5 @@
+from math import sqrt
+
 n = input("Masukan angka: ")
 str_n = str(n)
 angka = []
@@ -9,12 +11,29 @@
 
 angka = list(dict.fromkeys(angka))
 
-def prime(n): 
+def prime(n: int): 
+    """
+    Function that checks whether an integer number is prime or not.
+    A prime number is a number which has two distinct divisors: itself and 1.
+
+    @param n: int 
+    @return: str
+
+    """
+    # first check if n is not negative.
     if n <= 0:
         return "Not defined" 
+
+    # 1 is not a prime
+    # note that 1 have only 1 distinct divisor which is itself.
     elif n == 1:
         return "Not prime" 
-    for i in range(2, n): 
+
+    # if n >= 2 then iterate through all numbers from 2 to the square root of n
+    # to check if there is another number that divide n
+    # note that we stopped at sqrt(n) since (i divide n) -> (i/n divide n) and either one of the two (i & n/i) is below sqrt(n)
+    for i in range(2, int(sqrt(n)) + 1):
+        # i divide n is equivalent to n%i == 0
         if n%i == 0:
             return "not prime" 
     return "prime"
@@ -24,4 +43,4 @@ def prime(n):
     if x == "prime":
         prima.append(a)
 
-print(prima)
+print(prima)