What is std::ranges::set_union and set operations (C++23)?

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**std::ranges** provides set operations for sorted ranges. ```cpp #include std::vector a = {1, 2, 3, 4}; std::vector b = {3, 4, 5, 6}; // Union auto uni = std::ranges::set_union(a, b); // 1, 2, 3, 4, 5, 6 // Intersection auto inter = std::ranges::set_intersection(a, b); // 3, 4 // Difference auto diff = std::ranges::set_difference(a, b); // 1, 2 // Symmetric difference auto sym = std::ranges::set_symmetric_difference(a, b); // 1, 2, 5, 6 // Inplace versions std::vector result; std::ranges::set_union(a, b, std::back_inserter(result)); // With custom comparator std::ranges::set_union(a, b, std::back_inserter(result), std::ranges::greater{}); // Includes if (std::ranges::includes(a, b)) { /* a contains all of b */ } // Must be sorted! std::ranges::sort(a); std::ranges::sort(b); ``` **Requirements:** - Ranges must be sorted. - O(n + m) complexity. - Works with any comparator.

C++: What is std::ranges::set_union and set operations (C++23)?