#include "leetcode.h" class Solution { public: int maxOperations(vector &nums, int k) { unordered_map freq; int ans = 0; for (int i = 0; i < nums.size(); i++) if (freq[k - nums[i]] > 0) { ans++; freq[k - nums[i]]--; } else freq[nums[i]]++; return ans; } }; int main() { vector nums = {1, 2, 3, 4}; Solution obj; cout << obj.maxOperations(nums, 5); }