Package edu.princeton.cs.algs4

Class BreadthFirstPaths

Object

edu.princeton.cs.algs4.BreadthFirstPaths

public class BreadthFirstPaths
extends Object

The BreadthFirstPaths class represents a data type for finding shortest paths (number of edges) from a source vertex s (or a set of source vertices) to every other vertex in an undirected graph.

This implementation uses breadth-first search. The constructor takes Θ(V + E) time in the worst case, where V is the number of vertices and E is the number of edges. Each instance method takes Θ(1) time. It uses Θ(V) extra space (not including the graph).

For additional documentation, see Section 4.1 of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.

Author:

Robert Sedgewick, Kevin Wayne

Constructor Summary

Constructors

Constructor	Description
BreadthFirstPaths(Graph graph, int s)	Computes the shortest path between the source vertex s and every other vertex in the undirected graph graph.
BreadthFirstPaths(Graph graph, Iterable<Integer> sources)	Computes the shortest path between any one of the source vertices in sources and every other vertex in graph.

Method Summary

Modifier and Type	Method	Description
int	distTo(int v)	Returns the number of edges in a shortest path between the source vertex s (or sources) and vertex v?
boolean	hasPathTo(int v)	Is there a path between the source vertex s (or sources) and vertex v?
static void	main(String[] args)	Unit tests the BreadthFirstPaths data type.
Iterable<Integer>	pathTo(int v)	Returns a shortest path between the source vertex s (or sources) and v, or null if no such path.

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BreadthFirstPaths

public BreadthFirstPaths(Graph graph,
                         int s)

Computes the shortest path between the source vertex s and every other vertex in the undirected graph graph.

Parameters:

graph - the graph

s - the source vertex

Throws:

IllegalArgumentException - unless 0 <= s < V

BreadthFirstPaths

public BreadthFirstPaths(Graph graph,
                         Iterable<Integer> sources)

Computes the shortest path between any one of the source vertices in sources and every other vertex in graph.

Parameters:

graph - the graph

sources - the source vertices

Throws:

IllegalArgumentException - if sources is null

IllegalArgumentException - if sources contains no vertices

IllegalArgumentException - unless 0 <= s < V for each vertex s in sources

Method Detail

hasPathTo

public boolean hasPathTo(int v)

Is there a path between the source vertex s (or sources) and vertex v?

Parameters:

v - the vertex

Returns:

true if there is a path, and false otherwise

Throws:

IllegalArgumentException - unless 0 <= v < V

distTo

public int distTo(int v)

Returns the number of edges in a shortest path between the source vertex s (or sources) and vertex v?

Parameters:

v - the vertex

Returns:

the number of edges in such a shortest path (or Integer.MAX_VALUE if there is no such path)

Throws:

IllegalArgumentException - unless 0 <= v < V

pathTo

public Iterable<Integer> pathTo(int v)

Returns a shortest path between the source vertex s (or sources) and v, or null if no such path.

Parameters:

v - the vertex

Returns:

the sequence of vertices on a shortest path, as an Iterable

Throws:

IllegalArgumentException - unless 0 <= v < V

main

public static void main(String[] args)

Unit tests the BreadthFirstPaths data type.

Parameters:

args - the command-line arguments