chore(CPlusPlus): add Recursive Prime Checker (#548)

Co-authored-by: Ming Tsai <37890026+ming-tsai@users.noreply.github.com>
Co-authored-by: Ujjwal <75884061+UG-SEP@users.noreply.github.com>

algorithms/CPlusPlus/README.md

@@ -137,4 +137,4 @@
 - [Sum of all elements of an array](Recursion/Sum-of-all-elements-in-an-array.cpp)
 - [Decimal number to Binary conversion](Recursion/decimal-to-binary-conversion.cpp)
 - [Sum of digits of a decimal integer](Recursion/sum-of-digits-of-an-integer.cpp)
-
+- [Prime Check](Recursion/recursive-prime.cpp)

algorithms/CPlusPlus/Recursion/recursive-prime.cpp

@@ -0,0 +1,72 @@
+/*
+Problem: Check if a given number is prime or not, using Recursion
+*/
+
+#include <bits/stdc++.h>
+using namespace std;
+ 
+// primeCheck is function that check whether the given number is prime or not and,
+// return true if prime else 
+// return false  
+
+bool primeCheck(int n, int i)
+{
+    // Base cases
+    if(n <= 2){ 
+        // 2 is a prime
+        if(n == 2){
+            return true;
+        }
+
+        // 0 and 1 are not prime
+        return false;
+    }
+
+    // if i divides n then n is not prime
+    if(n % i == 0){
+        return false;
+    }
+
+    if(i * i > n){
+        return true;
+    }
+ 
+    // Check for next possible divisor
+    return primeCheck(n, i + 1);
+}
+ 
+// Main
+int main()
+{
+    cout << "Enter the number to check prime : " << endl;
+    int n;
+    cin >> n;
+
+    //check and output
+    if (primeCheck(n, 2))
+        cout << "YES" <<endl;
+    else
+        cout << "NO" <<endl;
+ 
+    return 0;
+}
+
+/*
+Time Complexity : O(sqrt(n))
+
+
+Input
+Enter the number to check prime : 5
+Output
+YES
+
+Input 
+Enter the number to check prime : 10
+Output
+NO
+
+Input 
+Enter the number to check prime : 33
+Output
+NO
+*/