Solution

CMakeLists.txt

@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 3.21)
+project(smallest_int)
+
+set(CMAKE_CXX_STANDARD 14)
+
+add_executable(smallest_int main.cpp)

main.cpp

@@ -0,0 +1,45 @@
+#include <iostream>
+
+// you can use includes, for example:
+// #include <algorithm>
+#include <bitset>
+#include <vector>
+#include <limits>
+
+constexpr size_t N_MAX_ELEMS = 1000000;
+
+// you can write to stdout for debugging purposes, e.g.
+// cout << "this is a debug message" << endl;
+
+int solution(std::vector<int> A) {
+
+    std::vector<uint64_t> ref(N_MAX_ELEMS/sizeof(uint64_t), 0);
+
+    for (auto elem : A) {
+        if (elem <= 0) {
+            continue;
+        }
+        ref[elem/8] |= (1 << (elem%8));
+    }
+
+    for (size_t i = 0; i < ref.size(); i++) {
+        if (ref[i] != std::numeric_limits<uint64_t>::max()) {
+            for (size_t j = 0; j < sizeof(uint64_t); j++) {
+                if (i == 0 && j == 0) {
+                    continue;
+                }
+                if ((ref[i]&(1 << j))==0) {
+                    return (i*8+j);
+                }
+            }
+        }
+    }
+
+    return N_MAX_ELEMS+1;
+}
+
+
+int main() {
+    std::cout << solution({1,3,4,5,1,6}) << std::endl;
+    return 0;
+}