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3237. Alt and Tab Simulation

  • Time: $O(n)$
  • Space: $O(n)$
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class Solution {
 public:
  vector<int> simulationResult(vector<int>& windows, vector<int>& queries) {
    vector<int> ans;
    unordered_set<int> seen;

    for (int i = queries.size() - 1; i >= 0; --i)
      if (!seen.contains(queries[i])) {
        ans.push_back(queries[i]);
        seen.insert(queries[i]);
      }

    for (const int window : windows)
      if (!seen.contains(window)) {
        ans.push_back(window);
        seen.insert(window);
      }

    return ans;
  }
};

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class Solution {
  public int[] simulationResult(int[] windows, int[] queries) {
    int[] ans = new int[windows.length];
    int ansIndex = 0;
    Set<Integer> seen = new HashSet<>();

    for (int i = queries.length - 1; i >= 0; --i)
      if (!seen.contains(queries[i])) {
        ans[ansIndex++] = queries[i];
        seen.add(queries[i]);
      }

    for (final int window : windows)
      if (!seen.contains(window)) {
        ans[ansIndex++] = window;
        seen.add(window);
      }

    return ans;
  }
}

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class Solution:
  def simulationResult(
      self,
      windows: list[int],
      queries: list[int],
  ) -> list[int]:
    ans = []
    seen = set()

    for query in reversed(queries):
      if query not in seen:
        ans.append(query)
        seen.add(query)

    for window in windows:
      if window not in seen:
        ans.append(window)
        seen.add(window)

    return ans