Package edu.princeton.cs.algs4

Class DijkstraUndirectedSP

  • public class DijkstraUndirectedSP
extends Object
    The DijkstraUndirectedSP class represents a data type for solving the single-source shortest paths problem in edge-weighted graphs where the edge weights are non-negative.

    This implementation uses Dijkstra's algorithm with a binary heap. The constructor takes Θ(E log V) 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 edge-weighted graph).

    For additional documentation, see Section 4.4 of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne. See DijkstraSP for a version on edge-weighted digraphs.

    This correctly computes shortest paths if all arithmetic performed is without floating-point rounding error or arithmetic overflow. This is the case if all edge weights are integers and if none of the intermediate results exceeds 252. Since all intermediate results are sums of edge weights, they are bounded by V C, where V is the number of vertices and C is the maximum weight of any edge.

    Author:
    Robert Sedgewick, Kevin Wayne, Nate Liu

    • Constructor Detail

      • DijkstraUndirectedSP

        public DijkstraUndirectedSP​(EdgeWeightedGraph G,
                            int s)
        Computes a shortest-paths tree from the source vertex s to every other vertex in the edge-weighted graph G.
        Parameters:
        G - the edge-weighted digraph
        s - the source vertex
        Throws:
        IllegalArgumentException - if an edge weight is negative
        IllegalArgumentException - unless 0 <= s < V

    • Method Detail

      • distTo

        public double distTo​(int v)
        Returns the length of a shortest path between the source vertex s and vertex v.
        Parameters:
        v - the destination vertex
        Returns:
        the length of a shortest path between the source vertex s and the vertex v; Double.POSITIVE_INFINITY if no such path
        Throws:
        IllegalArgumentException - unless 0 <= v < V

      • hasPathTo

        public boolean hasPathTo​(int v)
        Returns true if there is a path between the source vertex s and vertex v.
        Parameters:
        v - the destination vertex
        Returns:
        true if there is a path between the source vertex s to vertex v; false otherwise
        Throws:
        IllegalArgumentException - unless 0 <= v < V

      • pathTo

        public Iterable<Edge> pathTo​(int v)
        Returns a shortest path between the source vertex s and vertex v.
        Parameters:
        v - the destination vertex
        Returns:
        a shortest path between the source vertex s and vertex v; null if no such path
        Throws:
        IllegalArgumentException - unless 0 <= v < V

      • main

        public static void main​(String[] args)
        Unit tests the DijkstraUndirectedSP data type.
        Parameters:
        args - the command-line arguments