// Exercise 4.1.16

package algs41;

import stdlib.*;

// This is problem 4.1.16 from the textbook

//

// You need only change the constructor.

// You can also change the main method.

// But you should not change eccentricity(), diameter(), radius(), center() or isCenter()

// You can (and should!) add more private methods (such as bfs or dfs)

//

// TODO: complete the following, using only Graph and GraphGenerator.

// You may copy code from other classes in algs41, but you should not use the classes themselves.

// In particular, you may not use BreadthFirstPaths although you may copy code from there.

//

// The "distance" from vertex v to vertex w is the length of the shortest path

// from v to w.

// The "eccentricity" of a vertex v is distance to the farthest vertex from v.

// The "diameter" of a graph is the maximum eccentricity of any vertex.

// The "radius" of a graph is the smallest eccentricity of any vertex.

// A "center" is a vertex whose eccentricity is the radius.

// The center is not necessarily unique.

public class MyGraphProperties {

int[] eccentricity;

int diameter;

int radius;

int center;

// Constructor can be linear in G.V() * G.E()

public MyGraphProperties(Graph G) {

this.eccentricity = new int[G.V()];

int diameter = Integer.MIN_VALUE;

int radius = Integer.MAX_VALUE;

int center = -1;

// If G.V()==0, then these are the correct values.

// If G is not connected, you should throw a new IllegalArgumentException()

// I suggest that you first get it to work for a connected graph

// This will require that you traverse the graph starting from some node (say 0)

// You can then adjust your code so that it throws an exception in the case that all nodes are not visited

// TODO

// compute the eccentricity, diameter, radius and center

// The center of the graph is not unique, set center to SOME center --- it does not matter which one

this.diameter = diameter;

this.radius = radius;

this.center = center;

}

// Do not change the following constant time methods

public int eccentricity(int v) { return eccentricity[v]; }

public int diameter() { return diameter; }

public int radius() { return radius; }

public int center() { return center; }

public boolean isCenter(int v) { return eccentricity[v] == radius; }

public static void main(String[] args) {

//Graph G = GraphGenerator.fromIn (new In("data/tinyG.txt")); // this is non-connected -- should throw an exception

//Graph G = GraphGenerator.connected (10, 20, 2); // Random non-connected graph -- should throw an exception

Graph G = GraphGenerator.fromIn (new In("data/tinyCG.txt")); // diameter=2, radius=2, every node is a center

//Graph G = GraphGenerator.binaryTree (10); // A complete binary tree

//Graph G = GraphGenerator.path (10); // A path -- diameter=V-1

//Graph G = GraphGenerator.connected (20, 400); // Random connected graph

StdOut.println(G);

G.toGraphviz ("g.png");

MyGraphProperties gp = new MyGraphProperties(G);

for (int v = 0; v < G.V(); v++)

StdOut.format ("eccentricity of %d: %d ", v, gp.eccentricity (v));

StdOut.format ("diameter=%d, radius=%d, center=%d ", gp.diameter(), gp.radius (), gp.center ());

}

}