utils: print a vector

includes/utils.hpp

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <iostream>
+#include <vector>
+
+template <typename T>
+void print_vec(std::vector<T> vec) {
+  std::cout << "[ (" << vec.size() << ")\n";
+  for (auto it : vec) {
+    std::cout << "  " << it << "\n";
+  }
+  std::cout << "]\n";
+}