Project: s41467-024-55639-3 | Function: k_core (cpp)

system: You are an expert C++ programmer implementing algorithms from scientific papers.
Complete the masked function based on the algorithm description.
Follow C++ best practices and maintain consistent code style.
Return **only** the complete C++ function code.

user: Complete this C++ function:

**DESCRIPTION:** Implements k-core percolation algorithm on hypergraphs to model cascading failures in complex networks, iteratively removing nodes with insufficient connections

**KEY TERMS:** {
  "kcore": "minimum degree threshold",
  "TBR": "nodes to be removed in cascade",
  "active": "node state (1=active, 0=failed)",
  "giant": "size of surviving component",
  "v": "hypergraph adjacency list",
  "degree": "number of active connections",
  "node1/node2": "connected nodes in hyperedge"
}

**CONTEXT CODE:** 
	vector<int> node_order;
	vector<double> giant_vec, p_vec;

	for(int i=0;i<n;i++)
		node_order.push_back(i);

	std::shuffle(node_order.begin(), node_order.end(), gen);

	int node_count = int(dp*n);
	giant_vec.push_back(1);
	p_vec.push_back(1);
	int count = 0;
	while(count<n){
		//for(int j = 0;j < count; j++){
		//	active[node_order[j]] = 0;
		//}
		for(int j = 0;j < node_count; j++){
			active[node_order[count]] = 0;
			count++;
		}
		double p = 1 - (double)count/n;
		p_vec.push_back(p);
		double giant = k_core(kcore);

		//for(int j = 0;j < n; j++){
		//	active[j] = 1;
		//}
		giant_vec.push_back(giant);
		cout<<"p = "<<p<<", giant = "<<giant<<endl;

	}

	ofstream dataInfo;
	stringstream ss;
	const char* cfile;
	string fileR = where_to + "/2core";
	ss<<TestNum;
	fileR = fileR + ss.str() + ".txt";
	cfile = fileR.c_str();
	dataInfo.open(cfile, ofstream::out);
	for(int i=0; i<p_vec.size();i++)
	{
		dataInfo<<p_vec[i]<<"	"<<giant_vec[i]<<endl;
	}

	dataInfo.close();

}

double HyperGraph::k_core(int kcore){
    std::cerr << "Function k_core has been masked" << std::endl;
    throw std::runtime_error("Function implementation has been masked");
    return -1.0;
}

double HyperGraph::k_core_avalanches2(int kcore, vector<double>& av_vec){

	vector<int> TBR;
	double giant = n;

	for(int i = 0; i < n; i++){
		if(active[i] == 0){
			giant--;
			continue;
		}

		int degree = 0;
		for(int j = 0; j < v[i].size(); j++){
			if(active[v[i][j].first] == 1 and active[v[i][j].second] == 1)
				degree++;

		}

		if(degree < kcore){
			TBR.push_back(i);
			active[i] = 0;
			giant--;
		}

	}

	av_vec.push_back(TBR.size());
	int counter_old = TBR.size(), counter_new = 0;
	while(TBR.size() != 0){

		int node = TBR.back();
		TBR.pop_back();
		counter_old--;
		for(int j = 0; j < v[node].size(); j++){


				int node1 = v[node][j].first;
				int node2 = v[node][j].second;

				if(active[node1] == 1){
					int degree = 0;
					for(int q = 0; q < v[node1].size(); q++){
						if(active[v[node1][q].first] == 1 and active[v[node1][q].second] == 1)
							degree++;
					}

					if(degree < kcore){
						TBR.push_back(node1);
						active[node1] = 0;
						counter_new++;
						giant--;
					}

				}

				if(active[node2] == 1){
					int degree = 0;
					for(int q = 0; q < v[node2].size(); q++){
						if(active[v[node2][q].first] == 1 and active[v[node2][q].second] == 1)
							degree++;
					}

					if(degree < kcore){
						TBR.push_back(node2);
						active[node2] = 0;
						counter_new++;
						giant--;
					}

				}
		}

		if(counter_old == 0){
			if(counter_new != 0)
				av_vec.push_back(counter_new);
			counter_old = counter_new;
			counter_new = 0;
		}

	}

		for(int i = 0; i < n; i++){
			if(active[i] == 0){
				continue;
			}

			int degree = 0;
			for(int j = 0; j < v[i].size(); j++){
				if(active[v[i][j].first] == 1 and active[v[i][j].second] == 1)
					degree++;

			}
			if(degree < kcore)
				cout<<"Error"<<endl;


Complete the function implementation replacing "throw std::runtime_error("Not implemented");".