Added intersection code for c++.

current/algorithms/intersection.cpp

@@ -0,0 +1,28 @@
+#include <algorithm>
+#include <iostream>
+#include <iterator>
+#include <set>
+#include <vector>
+
+int main() {
+  std::set<int> v1{7, 2, 3, 4, 5, 6, 7, 8};
+  std::set<int> v2{5, 7, 9, 7};
+  // sorting is important for lists if we do want all elements of intersections (f.e. if the elements are not unique in both lists)
+  // std::sort(v1.begin(), v1.end());
+  // std::sort(v2.begin(), v2.end());
+
+  std::set<int> v_intersection;
+
+  std::set_intersection(
+      v1.begin(), v1.end(), 
+      v2.begin(), v2.end(),
+      std::inserter(v_intersection, v_intersection.begin()));
+      // std::back_inserter(v_intersection))); // for vector / list
+
+  for (auto n: v_intersection) {
+    std::cout << "n: " << n << std::endl;
+  }
+
+  std::cout << std::endl;
+  return 0;
+}