Set Intersection Size At Least Two.cpp

// Runtime: 56 ms (Top 88.46%) | Memory: 17.8 MB (Top 31.41%)
class Solution {
public:

    // sort wrt. end value

    static bool compare(vector<int>& a, vector<int>& b)
    {
        if(a[1] == b[1])
            return a[0] < b[0];
        else
            return a[1] < b[1];
    }

    int intersectionSizeTwo(vector<vector<int>>& intervals) {

        int n = intervals.size();

        // sort the array

        sort(intervals.begin(), intervals.end(), compare);

        vector<int> res;

        res.push_back(intervals[0][1] - 1);

        res.push_back(intervals[0][1]);

        for(int i = 1; i < n; i++)
        {
            int start = intervals[i][0];

            int end = intervals[i][1];

            if(start > res.back())
            {
                res.push_back(end - 1);

                res.push_back(end);
            }
            else if(start == res.back())
            {
                res.push_back(end);
            }
            else if(start > res[res.size() - 2])
            {
                res.push_back(end);
            }
        }

        return res.size();
    }
};