Hello,

I am really facing difficulty while solving tasks that require some observations to be made. Even though I solve many tasks related to them. Whenever I solve a new task again I end up thinking and not able to proceed any further. What can be done in order to improve my ability to draw neat and correct observations? How do you tackle this problem if you were in my situation?

Thanks.

Hello, I was solving some classical problems in UVA, now I am stuck on this task.

315 Network

A Telephone Line Company (TLC) is establishing a new telephone cable network. They are connecting
several places numbered by integers from 1 to N. No two places have the same number. The lines
are bidirectional and always connect together two places and in each place, the lines end in a telephone
exchange. There is one telephone exchange in each place. From each place it is possible to reach through
lines every other place, however, it need not be a direct connection, it can go through several exchanges.
From time to time the power supply fails at a place and then the exchange does not operate. The
officials from TLC realized that in such a case it can happen that besides the fact that the place with
the failure is unreachable, this can also cause that some other places cannot connect to each other. In
such a case we will say the place (where the failure occurred) is critical. Now the officials are trying to
write a program for finding the number of all such critical places. Help them.

Input
The input file consists of several blocks of lines. Each block describes one network. In the first line
of each block, there is the number of places N < 100. Each of the next at most N lines contains the
number of a place followed by the numbers of some places to which there is a direct line from this place.
These at most N lines completely describe the network, i.e., each direct connection of two places in the
network is contained at least in one row. All numbers in one line are separated by one space. Each
block ends with a line containing just ‘0’. The last block has only one line with N = 0.

Output
The output contains for each block except the last in the input file one line containing the number of
critical places.

Sample Input
5
5 1 2 3 4
0
6
2 1 3
5 4 6 2
0
0

Sample Output
1
2

I know that we need to count the number of articulation points and report it. But before that, I didn't even understand how to take the input. So can anyone help me by giving some advice on input and output formatting not only for this task but in general?

I am sorry if the problem statement is not readable. I don't know how to post a task as others do.

Hello everyone, I was solving this Problem 20C - Dijkstra? and wrote a code and submitted but it gave me a TLE on test 28. Can I still improve my code's efficiency? I am not able to figure it out how to do so. Thanks.

#include<bits/stdc++.h>
using namespace std;
typedef pair<int,int> pii;
typedef vector<pii> vii;
typedef vector<int> vi;
#define inf 0x3f3f3f3f

vii *G;
vi D,P;

void Dijkstra(int s,int N){
	D.assign(N+1,inf);
	P.assign(N+1,-1);
	D[s]=0;
	P[s]=-1;
	set<pii> Q;
	Q.insert({s,0});
	while(!Q.empty()){
		auto top=Q.begin();
		int u=top->first;
		Q.erase(top);
		if(u==N)return ;
		for(auto next:G[u]){
			int v=next.first,wt=next.second;
			if(D[v]>D[u]+wt){
				P[v]=u;
				Q.erase({v,D[v]});
				D[v]=D[u]+wt;
				Q.insert({v,D[v]});
			}
		}
	}
}
void print_shortest_path(int to){
	vi path;
	for(int i=to;i!=-1;i=P[i])path.push_back(i);
	reverse(path.begin(),path.end());
	for(auto i:path)cout<<i<<" ";
}
int main(){
	int N,m;cin>>N>>m;
	G= new vii[N+1];
	for(int i=0;i<m;i++){
		int a,b,w;cin>>a>>b>>w;
		G[a].push_back({b,w});
		G[b].push_back({a,w});
	}
	Dijkstra(1,N);
	if(D[N]==inf)cout<<-1;
	else
		print_shortest_path(N);
	//cout<<D[N]<<"\n";
		
}