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class Solution {
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 public:
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  // sort wrt. end value
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  static bool compare(vector<int> &a, vector<int> &b) {
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    if (a[1] == b[1])
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      return a[0] < b[0];
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    else
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      return a[1] < b[1];
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  }
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  int intersectionSizeTwo(vector<vector<int>> &intervals) {
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    int n = intervals.size();
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    // sort the array
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    sort(intervals.begin(), intervals.end(), compare);
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    vector<int> res;
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    res.push_back(intervals[0][1] - 1);
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    res.push_back(intervals[0][1]);
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    for (int i = 1; i < n; i++) {
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      int start = intervals[i][0];
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      int end = intervals[i][1];
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      if (start > res.back()) {
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        res.push_back(end - 1);
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        res.push_back(end);
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      } else if (start == res.back()) {
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        res.push_back(end);
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      } else if (start > res[res.size() - 2]) {
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        res.push_back(end);
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      }
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    }
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    return res.size();
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  }
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};