194 lines
7.2 KiB
Java
194 lines
7.2 KiB
Java
|
|
||
|
|
|
||
|
|
import edu.princeton.cs.introcs.StdOut;
|
||
|
|
|
||
|
|
/*************************************************************************
|
||
|
|
* Compilation: javac FlowEdge.java
|
||
|
|
* Execution: java FlowEdge
|
||
|
|
*
|
||
|
|
* Capacitated edge with a flow in a flow network.
|
||
|
|
*
|
||
|
|
*************************************************************************/
|
||
|
|
|
||
|
|
/**
|
||
|
|
* The FlowEdge 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.
|
||
|
|
*
|
||
|
|
* For additional documentation, see <a href="http://algs4.cs.princeton.edu/64maxflow">Section 6.4</a> of
|
||
|
|
* Algorithms, 4th Edition 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 v to vertex w with
|
||
|
|
* the given capacity 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 v or w
|
||
|
|
* is a negative integer
|
||
|
|
* @throws java.lang.IllegalArgumentException if capacity 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 v to vertex w with
|
||
|
|
* the given capacity and flow .
|
||
|
|
* @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 v or w
|
||
|
|
* is a negative integer
|
||
|
|
* @throws java.lang.IllegalArgumentException if capacity is negative
|
||
|
|
* @throws java.lang.IllegalArgumentException unless flow is between
|
||
|
|
* 0.0 and capacity .
|
||
|
|
*/
|
||
|
|
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 vertex 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 vertex .
|
||
|
|
* @param vertex one endpoint of the edge
|
||
|
|
* @return the residual capacity of the edge in the direction to the given vertex
|
||
|
|
* If vertex is the tail vertex, the residual capacity equals
|
||
|
|
* capacity() - flow() ; if vertex is the head vertex, the
|
||
|
|
* residual capacity equals flow() .
|
||
|
|
* @throws java.lang.IllegalArgumentException if vertex 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 vertex is the tail vertex, this increases the flow on the edge by delta ;
|
||
|
|
* if vertex is the head vertex, this decreases the flow on the edge by delta .
|
||
|
|
* @param vertex one endpoint of the edge
|
||
|
|
* @throws java.lang.IllegalArgumentException if vertex is not one of the endpoints
|
||
|
|
* of the edge
|
||
|
|
* @throws java.lang.IllegalArgumentException if delta makes the flow on
|
||
|
|
* on the edge either negative or larger than its capacity
|
||
|
|
* @throws java.lang.IllegalArgumentException if delta is NaN
|
||
|
|
*/
|
||
|
|
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
|
||
|
|
*/
|
||
|
|
@Override
|
||
|
|
public String toString() {
|
||
|
|
return v + "->" + w + " " + flow + "/" + capacity;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Unit tests the FlowEdge data type.
|
||
|
|
*/
|
||
|
|
public static void main(String[] args) {
|
||
|
|
FlowEdge e = new FlowEdge(12, 23, 3.14);
|
||
|
|
StdOut.println(e);
|
||
|
|
}
|
||
|
|
|
||
|
|
}
|