757.cpp

#include <bits/stdc++.h>
using namespace std;
int intersectionSizeTwo(vector<vector<int>>& intervals) {
    sort(intervals.begin(), intervals.end(), [](auto &a, auto &b){
    if (a[1] == b[1]) return a[0] > b[0];
        return a[1] < b[1];
    });

    vector<int> nums; 

    int a = -1, b = -1;

    for (auto &in : intervals) {
        int start = in[0];
        int end = in[1];

        bool hasA = (a >= start && a <= end);
        bool hasB = (b >= start && b <= end);

        if (hasA && hasB) continue;          
        else if (hasB) {                    
        
            int x = end;
            nums.push_back(x);
            a = b;
            b = x;
        }
        else if (hasA) {                  
            nums.push_back(end - 1);
            nums.push_back(end);

            b = end;
            a = end - 1;
        }
        else {               
            nums.push_back(end - 1);
            nums.push_back(end);

            a = end - 1;
            b = end;
        }
    }

    return nums.size();
}
int main() {
    vector<vector<int>> intervals = {{1, 3}, {1, 4}, {2, 5}, {3, 5}};
    cout << intersectionSizeTwo(intervals) << endl;
    return 0;
}