Fix tiny text tweaks

Author: linouk23

Combinatorics/README.markdown

@@ -358,17 +358,17 @@ binomialCoefficient(30, 15)   // prints 155117520
 binomialCoefficient(66, 33)   // prints a very large number
 ```
 
-There's a faster approach to calculate `C(n, k)` in 'O(k)' time and 'O(1)' extra space.
+There's a faster approach to calculate `C(n, k)` in `O(k) time and `O(1)` extra space.
 
 The idea behind it is that the formula for `C(n, k)` is:
 
                    n!                      n * (n - 1) * ... * 1
     C(n, k) = ------------- = ------------------------------------------
               (n - k)! * k!      (n - k) * (n - k - 1) * ... * 1 * k!
 
-After reduction of fractions, we get the following formula:
+After the reduction of fractions, we get the following formula:
 
-                   n * (n - 1) * ... * (n - k + 1)         (n - 0) * (n - 1) * ... * (n - k + 1)  
+                   n * (n - 1) * ... * (n - k + 1)         (n - 0) * (n - 1) * ... * (n - k + 1)
     C(n, k) = --------------------------------------- = -----------------------------------------
                                k!                          (k - 0) * (k - 1) * ... * 1
 
@@ -377,7 +377,7 @@ So the following code calculates the `C(n, k)` you're looking for:
 ```swift
 func quickBinomialCoefficient(n: Int, _ k: Int) -> Int {
   var result = 1
-    
+
   for i in 0..<k {
     result *= (n - i)
     result /=  (i + 1)
@@ -388,7 +388,7 @@ func quickBinomialCoefficient(n: Int, _ k: Int) -> Int {
 
 As there're the divisors for numbers from '1...k' among 'k' consecutive numbers, what is exactly we've got in the numerator of our fast formula every time we devide 'result' by '(i + 1)' we won't have a real number.
 
-Now you can calculate `C(30, 15)` without any problems:
+Here's how you can use it:
 
 ```swift
 quickbinomialCoefficient(30, 15)   // prints 155117520