package edu.princeton.cs.algs4;
import edu.princeton.cs.introcs.*;
/*************************************************************************
* Compilation: javac FlowEdge.java
* Execution: java FlowEdge
*
* Capacitated edge with a flow in a flow network.
*
*************************************************************************/
/**
* The <tt>FlowEdge</tt> class represents a capacitated edge with a
* flow in a {@link FlowNetwork}. Each edge consists of two integers
* (naming the two vertices), a real-valued capacity, and a real-valued
* flow. The data type provides methods for accessing the two endpoints
* of the directed edge and the weight. It also provides methods for
* changing the amount of flow on the edge and determining the residual
* capacity of the edge.
* <p>
* For additional documentation, see <a href="http://algs4.cs.princeton.edu/64maxflow">Section 6.4</a> of
* <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class FlowEdge {
private final int v; // from
private final int w; // to
private final double capacity; // capacity
private double flow; // flow
/**
* Initializes an edge from vertex <tt>v</tt> to vertex <tt>w</tt> with
* the given <tt>capacity</tt> and zero flow.
* @param v the tail vertex
* @param w the head vertex
* @param capacity the capacity of the edge
* @throws java.lang.IndexOutOfBoundsException if either <tt>v</tt> or <tt>w</tt>
* is a negative integer
* @throws java.lang.IllegalArgumentException if <tt>capacity</tt> is negative
*/
public FlowEdge(int v, int w, double capacity) {
if (v < 0) throw new IndexOutOfBoundsException("Vertex name must be a nonnegative integer");
if (w < 0) throw new IndexOutOfBoundsException("Vertex name must be a nonnegative integer");
if (!(capacity >= 0.0)) throw new IllegalArgumentException("Edge capacity must be nonnegaitve");
this.v = v;
this.w = w;
this.capacity = capacity;
this.flow = 0.0;
}
/**
* Initializes an edge from vertex <tt>v</tt> to vertex <tt>w</tt> with
* the given <tt>capacity</tt> and <tt>flow</tt>.
* @param v the tail vertex
* @param w the head vertex
* @param capacity the capacity of the edge
* @param flow the flow on the edge
* @throws java.lang.IndexOutOfBoundsException if either <tt>v</tt> or <tt>w</tt>
* is a negative integer
* @throws java.lang.IllegalArgumentException if <tt>capacity</tt> is negative
* @throws java.lang.IllegalArgumentException unless <tt>flow</tt> is between
* <tt>0.0</tt> and <tt>capacity</tt>.
*/
public FlowEdge(int v, int w, double capacity, double flow) {
if (v < 0) throw new IndexOutOfBoundsException("Vertex name must be a nonnegative integer");
if (w < 0) throw new IndexOutOfBoundsException("Vertex name must be a nonnegative integer");
if (!(capacity >= 0.0)) throw new IllegalArgumentException("Edge capacity must be nonnegaitve");
if (!(flow <= capacity)) throw new IllegalArgumentException("Flow exceeds capacity");
if (!(flow >= 0.0)) throw new IllegalArgumentException("Flow must be nonnnegative");
this.v = v;
this.w = w;
this.capacity = capacity;
this.flow = flow;
}
/**
* Initializes a flow edge from another flow edge.
* @param e the edge to copy
*/
public FlowEdge(FlowEdge e) {
this.v = e.v;
this.w = e.w;
this.capacity = e.capacity;
this.flow = e.flow;
}
/**
* Returns the tail vertex of the edge.
* @return the tail vertex of the edge
*/
public int from() {
return v;
}
/**
* Returns the head vertex of the edge.
* @return the head vertex of the edge
*/
public int to() {
return w;
}
/**
* Returns the capacity of the edge.
* @return the capacity of the edge
*/
public double capacity() {
return capacity;
}
/**
* Returns the flow on the edge.
* @return the flow on the edge
*/
public double flow() {
return flow;
}
/**
* Returns the endpoint of the edge that is different from the given vertex
* (unless the edge represents a self-loop in which case it returns the same vertex).
* @param vertex one endpoint of the edge
* @return the endpoint of the edge that is different from the given vertex
* (unless the edge represents a self-loop in which case it returns the same vertex)
* @throws java.lang.IllegalArgumentException if <tt>vertex</tt> is not one of the endpoints
* of the edge
*/
public int other(int vertex) {
if (vertex == v) return w;
else if (vertex == w) return v;
else throw new IllegalArgumentException("Illegal endpoint");
}
/**
* Returns the residual capacity of the edge in the direction
* to the given <tt>vertex</tt>.
* @param vertex one endpoint of the edge
* @return the residual capacity of the edge in the direction to the given vertex
* If <tt>vertex</tt> is the tail vertex, the residual capacity equals
* <tt>capacity() - flow()</tt>; if <tt>vertex</tt> is the head vertex, the
* residual capacity equals <tt>flow()</tt>.
* @throws java.lang.IllegalArgumentException if <tt>vertex</tt> is not one of the endpoints
* of the edge
*/
public double residualCapacityTo(int vertex) {
if (vertex == v) return flow; // backward edge
else if (vertex == w) return capacity - flow; // forward edge
else throw new IllegalArgumentException("Illegal endpoint");
}
/**
* Increases the flow on the edge in the direction to the given vertex.
* If <tt>vertex</tt> is the tail vertex, this increases the flow on the edge by <tt>delta</tt>;
* if <tt>vertex</tt> is the head vertex, this decreases the flow on the edge by <tt>delta</tt>.
* @param vertex one endpoint of the edge
* @throws java.lang.IllegalArgumentException if <tt>vertex</tt> is not one of the endpoints
* of the edge
* @throws java.lang.IllegalArgumentException if <tt>delta</tt> makes the flow on
* on the edge either negative or larger than its capacity
* @throws java.lang.IllegalArgumentException if <tt>delta</tt> is <tt>NaN</tt>
*/
public void addResidualFlowTo(int vertex, double delta) {
if (vertex == v) flow -= delta; // backward edge
else if (vertex == w) flow += delta; // forward edge
else throw new IllegalArgumentException("Illegal endpoint");
if (Double.isNaN(delta)) throw new IllegalArgumentException("Change in flow = NaN");
if (!(flow >= 0.0)) throw new IllegalArgumentException("Flow is negative");
if (!(flow <= capacity)) throw new IllegalArgumentException("Flow exceeds capacity");
}
/**
* Returns a string representation of the edge.
* @return a string representation of the edge
*/
public String toString() {
return v + "->" + w + " " + flow + "/" + capacity;
}
/**
* Unit tests the <tt>FlowEdge</tt> data type.
*/
public static void main(String[] args) {
FlowEdge e = new FlowEdge(12, 23, 3.14);
StdOut.println(e);
}
}
/*************************************************************************
* Copyright 2002-2012, Robert Sedgewick and Kevin Wayne.
*
* This file is part of algs4-package.jar, which accompanies the textbook
*
* Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,
* Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.
* http://algs4.cs.princeton.edu
*
*
* algs4-package.jar is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* algs4-package.jar is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with algs4-package.jar. If not, see http://www.gnu.org/licenses.
*************************************************************************/