Sets in C++ STL (#369)

* Create Heap Sort in C++

* Codeforces solution of problem 49A

* Create Sets in c++ STL

Author: aishalxgupta

CPP/stl/Sets in c++ STL

@@ -0,0 +1,74 @@
+// CPP program to demonstrate various functions of
+// Set in C++ STL
+#include <iostream>
+#include <iterator>
+#include <set>
+using namespace std;
+ 
+int main()
+{
+    // empty set container
+    set<int, greater<int> > s1;
+ 
+    // insert elements in random order
+    s1.insert(40);
+    s1.insert(30);
+    s1.insert(60);
+    s1.insert(20);
+    s1.insert(50);
+ 
+    // only one 50 will be added to the set
+    s1.insert(50);
+    s1.insert(10);
+ 
+    // printing set s1
+    set<int, greater<int> >::iterator itr;
+    cout << "\nThe set s1 is : \n";
+    for (itr = s1.begin(); itr != s1.end(); itr++) {
+        cout << *itr << " ";
+    }
+    cout << endl;
+ 
+    // assigning the elements from s1 to s2
+    set<int> s2(s1.begin(), s1.end());
+ 
+    // print all elements of the set s2
+    cout << "\nThe set s2 after assign from s1 is : \n";
+    for (itr = s2.begin(); itr != s2.end(); itr++) {
+        cout << *itr << " ";
+    }
+    cout << endl;
+ 
+    // remove all elements up to 30 in s2
+    cout << "\ns2 after removal of elements less than 30 "
+            ":\n";
+    s2.erase(s2.begin(), s2.find(30));
+    for (itr = s2.begin(); itr != s2.end(); itr++) {
+        cout << *itr << " ";
+    }
+ 
+    // remove element with value 50 in s2
+    int num;
+    num = s2.erase(50);
+    cout << "\ns2.erase(50) : ";
+    cout << num << " removed\n";
+    for (itr = s2.begin(); itr != s2.end(); itr++) {
+        cout << *itr << " ";
+    }
+ 
+    cout << endl;
+ 
+    // lower bound and upper bound for set s1
+    cout << "s1.lower_bound(40) : \n"
+         << *s1.lower_bound(40) << endl;
+    cout << "s1.upper_bound(40) : \n"
+         << *s1.upper_bound(40) << endl;
+ 
+    // lower bound and upper bound for set s2
+    cout << "s2.lower_bound(40) :\n"
+         << *s2.lower_bound(40) << endl;
+    cout << "s2.upper_bound(40) : \n"
+         << *s2.upper_bound(40) << endl;
+ 
+    return 0;
+}