How do I binary search with algorithms with std::unordered_map?

Binary search typically requires a sorted sequence to function correctly. However, when working with `std::unordered_map`, the elements are not stored in any sorted order, making traditional binary search not directly applicable. Instead, to perform a binary search-like operation, you could first sort the keys and then implement a binary search over that sorted list. Below is an example illustrating how this approach can be implemented in C++.

#include #include #include #include // Function to perform binary search bool binarySearch(const std::vector& sortedKeys, int target) { int left = 0; int right = sortedKeys.size() - 1; while (left <= right) { int mid = left + (right - left) / 2; if (sortedKeys[mid] == target) return true; // Found else if (sortedKeys[mid] < target) left = mid + 1; // Search right else right = mid - 1; // Search left } return false; // Not found } int main() { std::unordered_map myMap = { {3, "Three"}, {1, "One"}, {4, "Four"}, {2, "Two"} }; // Create a vector of keys and sort it std::vector keys; for (const auto& pair : myMap) { keys.push_back(pair.first); } std::sort(keys.begin(), keys.end()); // Attempt to search for a key using binary search int target = 2; bool found = binarySearch(keys, target); std::cout << (found ? "Found" : "Not Found") << std::endl; return 0; }

Keywords: C++ binary search std::unordered_map sorting algorithms

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