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class Solution {
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 public:
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  bool isRectangleCover(vector<vector<int>> &rectangles) {
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    unordered_map<long long, int> mark;
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    const long long N = 1000000;
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    for (vector<int> &x : rectangles) {
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      int x1 = x[0];
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      int y1 = x[1];
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      int x2 = x[2];
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      int y2 = x[3];
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      mark[x1 * N + y1]++;
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      mark[x1 * N + y2]--;
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      mark[x2 * N + y1]--;
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      mark[x2 * N + y2]++;
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    }
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    int n_mark = 0;
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    for (auto ptr = mark.begin(); ptr != mark.end(); ptr++)
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      if (ptr->second != 0) {
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        if (abs(ptr->second) != 1) return false;
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        n_mark++;
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      }
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    return n_mark == 4;
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  }
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};