What is the difference between std::lower_bound and std::upper_bound?

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**lower_bound** — first >= value. **upper_bound** — first > value. ```cpp std::vector v = {1, 2, 2, 2, 3, 4}; // lower_bound — first >= 2 auto lb = std::lower_bound(v.begin(), v.end(), 2); // Points to first 2 (index 1) // upper_bound — first > 2 auto ub = std::upper_bound(v.begin(), v.end(), 2); // Points to 3 (index 4) // Range of 2s auto range = std::equal_range(v.begin(), v.end(), 2); // range.first = lb, range.second = ub std::cout << std::distance(range.first, range.second); // 3 (three 2s) ``` **Use cases:** - Range queries. - Counting occurrences. - Binary search on sorted data.

C++: What is the difference between std::lower_bound and std::upper_bound?