chore(CPlusPlus): created prime-check (#295)

* Created prime-check.cpp

Added new file in Maths section(prime-check.cpp).

* Updated Time complexity and addded test case.

Fixes indentation and minor typos.

* Fixed Indentation

* Fixed Indentation

* Updated Maths Section

* Fixed Typo

algorithms/CPlusPlus/Maths/prime-check.cpp

@@ -0,0 +1,29 @@
+#include<bits/stdc++.h>
+using namespace std;
+//Function to check whether a number is prime or not.
+bool isPrime(int num) {
+    if (num == 1)
+        return false;
+    if (num == 2 || num == 3)
+        return true;
+    if (num % 2 == 0 || num % 3 == 0)
+        return false; //Multiples of prime numbers are not prime
+    for (int i = 6; i * i <= num; i += 5) {
+        //If number is a composite  number then it must have one multiple greater(or equal) 
+        //to sqrt(num) and one multiple less(or equal) to sqrt(num).
+        //If the num doesn't satisfy the above conditions then the number is said to be a prime number
+        //Also prime number appear in the form of 6n-1 and 6n+1 where n is a natural number
+        if ((num % (i - 1) == 0) || (num % (i + 1) == 0))
+            return false;
+    }
+    return true;
+}
+int main() {
+    int num;
+    cin >> num; //Taking input from user
+    string result = isPrime(num) ? "Prime" : "Not Prime"; //Evaluating string based on result from isPrime function
+    cout << result; //Printing result
+    //Ex : num = 11 , result will print "Prime"
+    //Time Complexity :O(sqrt(num))
+    return 0;
+}

algorithms/CPlusPlus/README.md

@@ -64,3 +64,4 @@
 
 # Maths
 1. [Kaprekar Number](Maths/Kaprekar-number.cpp)
+2. [Prime Number](Maths/prime-check.cpp)