I'm learning graphs these days and need to clear few doubts-

1. Can I determine weather 5 points in two dimensions whose X and Y coordinates are given lie on the same straight line in O(1).
2. What is the efficient way to find out the degree of the specified vertex in an undirected graph (V,E)? I'm thinking of O(|E|)?
3. What is the efficient way to find degrees of all vertices in an undirected graph (V,E)? I'm think of O(|V||E|)
4. if |E| ≥ |V| can I say grapgh will be have guaranteed Euler circuit?
5. Is it possible to find slope of a straight line in O(1)time given the X and Y coordinates of n points on the line?