Klee's_algorithm

// C++ program to implement Klee's algorithm 
#include<bits/stdc++.h> 
using namespace std; 

// Returns sum of lengths covered by union of given 
// segments 
int segmentUnionLength(const vector <pair <int,int> > &seg) 
{ 
	int n = seg.size(); 

	// Create a vector to store starting and ending 
	// points 
	vector <pair <int, bool> > points(n * 2); 
	for (int i = 0; i < n; i++) 
	{ 
		points[i*2]	 = make_pair(seg[i].first, false); 
		points[i*2 + 1] = make_pair(seg[i].second, true); 
	} 

	// Sorting all points by point value 
	sort(points.begin(), points.end()); 

	int result = 0; // Initialize result 

	// To keep track of counts of current open segments 
	// (Starting point is processed, but ending point 
	// is not) 
	int Counter = 0; 

	// Trvaerse through all points 
	for (unsigned i=0; i<n*2; i++) 
	{ 
		// If there are open points, then we add the 
		// difference between previous and current point. 
		// This is interesting as we don't check whether 
		// current point is opening or closing, 
		if (Counter) 
			result += (points[i].first - points[i-1].first); 

		// If this is an ending point, reduce, count of 
		// open points. 
		(points[i].second)? Counter-- : Counter++; 
	} 
	return result; 
} 

// Driver program for the above code 
int main() 
{ 
	vector< pair <int,int> > segments; 
	segments.push_back(make_pair(3, 15)); 
	segments.push_back(make_pair(2, 5)); 
	segments.push_back(make_pair(4, 8)); 
	segments.push_back(make_pair(9, 12)); 
	cout << "Length of Union of All segments = "; 
	cout << segmentUnionLength(segments) << endl; 
	return 0; 
} 

I am commenting here because I thought SWE are more active on github than youtube.
I just wan't to know, What is the difference between klee's Algorithm and algorithm used in merge Interval question.

Can, I can use the concept of merge interval question to solve the this problem