P7Yb6w - Online C++ Compiler & Debugging Tool

#include <iostream>
#include <vector>
#include <map>
#include <algorithm>

using namespace std;

int maxEqualSubsequenceLength(vector<int>& arr, int k) {
    map<int, int> freqMap;

    // Calculate the ranges and fill the frequency map
    for (int num : arr) {
        freqMap[num - k]++; // Start of the range
        freqMap[num + k + 1]--; // End of the range + 1
    }

    int maxLength = 0;
    int currentLength = 0;

    // Compute prefix sums
    for (auto& entry : freqMap) {
        currentLength += entry.second; // Update current length
        maxLength = max(maxLength, currentLength); // Update max length
    }

    return maxLength;
}

int main() {
    vector<int> arr = {1, 2, 3, 4, 5};
    int k = 1;
    cout << "Maximum length of equal subsequence: " << maxEqualSubsequenceLength(arr, k) << endl;
    return 0;
}