Lecture 49 :- Missing Elements From An Array with Duplicates

To find the missing elements from an array that contains duplicates, you can use a hash map to keep track of the frequency of each element in the array. Then, you can iterate through the range of elements (from the minimum to the maximum) and check if the element is present in the hash map. If the element is not found or its frequency is less than the expected frequency, it means the element is missing.

Here's the C++ code to find the missing elements from an array with duplicates:

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#include <iostream> #include <vector> #include <unordered_map> std::vector<int> findMissingElements(std::vector<int>& nums) {    std::unordered_map<int, int> frequencyMap;    std::vector<int> missingElements;    // Calculate the frequency of each element in the array    for (int num : nums) {        frequencyMap[num]++;    }    // Find the minimum and maximum elements in the array    int minElement = *std::min_element(nums.begin(), nums.end());    int maxElement = *std::max_element(nums.begin(), nums.end());    // Check for missing elements in the range (minElement, maxElement)    for (int num = minElement; num <= maxElement; num++) {        if (frequencyMap.find(num) == frequencyMap.end() || frequencyMap[num] == 0) {            missingElements.push_back(num);        }    }    return missingElements; } int main() {    std::vector<int> nums = {4, 2, 2, 3, 6, 8, 8};    std::vector<int> missingElements = findMissingElements(nums);    if (!missingElements.empty()) {        std::cout << "Missing elements:";        for (int element : missingElements) {            std::cout << " " << element;        }        std::cout << std::endl;    } else {        std::cout << "No missing elements found." << std::endl;    }    return 0; }

Example Output:

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Missing elements: 5 7

In this code, the findMissingElements function calculates the frequency of each element using a hash map and then checks for missing elements in the range (minElement, maxElement). The time complexity of this approach is O(n), where n is the number of elements in the array.