some more solves

contests/6contest/4.cpp

@@ -0,0 +1,16 @@
+#include <set>
+
+template <typename It1, typename It2>
+It2 myremove(It1 first1, It1 last1, It2 first2, It2 last2) {
+    std::set to_remove(first1, last1);
+    It2 result = first2;
+
+    for (It2 it = first2; it != last2; ++it) {
+        if (to_remove.find(std::distance(first2, it)) == to_remove.end()) {
+            std::iter_swap(result, it);
+            ++result;
+        }
+    }
+
+    return result;
+}