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/*
* Copyright (C) 2017 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.graph;
import java.util.Set;
/**
* A non-public interface for the methods shared between {@link Graph} and {@link ValueGraph}.
*
* @author James Sexton
* @param <N> Node parameter type
*/
interface BaseGraph<N> extends SuccessorsFunction<N>, PredecessorsFunction<N> {
//
// Graph-level accessors
//
/** Returns all nodes in this graph, in the order specified by {@link #nodeOrder()}. */
Set<N> nodes();
/** Returns all edges in this graph. */
Set<EndpointPair<N>> edges();
//
// Graph properties
//
/**
* Returns true if the edges in this graph are directed. Directed edges connect a {@link
* EndpointPair#source() source node} to a {@link EndpointPair#target() target node}, while
* undirected edges connect a pair of nodes to each other.
*/
boolean isDirected();
/**
* Returns true if this graph allows self-loops (edges that connect a node to itself). Attempting
* to add a self-loop to a graph that does not allow them will throw an {@link
* IllegalArgumentException}.
*/
boolean allowsSelfLoops();
/** Returns the order of iteration for the elements of {@link #nodes()}. */
ElementOrder<N> nodeOrder();
//
// Element-level accessors
//
/**
* Returns the nodes which have an incident edge in common with {@code node} in this graph.
*
* @throws IllegalArgumentException if {@code node} is not an element of this graph
*/
Set<N> adjacentNodes(N node);
/**
* Returns all nodes in this graph adjacent to {@code node} which can be reached by traversing
* {@code node}'s incoming edges <i>against</i> the direction (if any) of the edge.
*
* <p>In an undirected graph, this is equivalent to {@link #adjacentNodes(Object)}.
*
* @throws IllegalArgumentException if {@code node} is not an element of this graph
*/
@Override
Set<N> predecessors(N node);
/**
* Returns all nodes in this graph adjacent to {@code node} which can be reached by traversing
* {@code node}'s outgoing edges in the direction (if any) of the edge.
*
* <p>In an undirected graph, this is equivalent to {@link #adjacentNodes(Object)}.
*
* <p>This is <i>not</i> the same as "all nodes reachable from {@code node} by following outgoing
* edges". For that functionality, see {@link Graphs#reachableNodes(Graph, Object)}.
*
* @throws IllegalArgumentException if {@code node} is not an element of this graph
*/
@Override
Set<N> successors(N node);
/**
* Returns the edges in this graph whose endpoints include {@code node}.
*
* @throws IllegalArgumentException if {@code node} is not an element of this graph
* @since 24.0
*/
Set<EndpointPair<N>> incidentEdges(N node);
/**
* Returns the count of {@code node}'s incident edges, counting self-loops twice (equivalently,
* the number of times an edge touches {@code node}).
*
* <p>For directed graphs, this is equal to {@code inDegree(node) + outDegree(node)}.
*
* <p>For undirected graphs, this is equal to {@code incidentEdges(node).size()} + (number of
* self-loops incident to {@code node}).
*
* <p>If the count is greater than {@code Integer.MAX_VALUE}, returns {@code Integer.MAX_VALUE}.
*
* @throws IllegalArgumentException if {@code node} is not an element of this graph
*/
int degree(N node);
/**
* Returns the count of {@code node}'s incoming edges (equal to {@code predecessors(node).size()})
* in a directed graph. In an undirected graph, returns the {@link #degree(Object)}.
*
* <p>If the count is greater than {@code Integer.MAX_VALUE}, returns {@code Integer.MAX_VALUE}.
*
* @throws IllegalArgumentException if {@code node} is not an element of this graph
*/
int inDegree(N node);
/**
* Returns the count of {@code node}'s outgoing edges (equal to {@code successors(node).size()})
* in a directed graph. In an undirected graph, returns the {@link #degree(Object)}.
*
* <p>If the count is greater than {@code Integer.MAX_VALUE}, returns {@code Integer.MAX_VALUE}.
*
* @throws IllegalArgumentException if {@code node} is not an element of this graph
*/
int outDegree(N node);
/**
* Returns true if there is an edge that directly connects {@code nodeU} to {@code nodeV}. This is
* equivalent to {@code nodes().contains(nodeU) && successors(nodeU).contains(nodeV)}.
*
* <p>In an undirected graph, this is equal to {@code hasEdgeConnecting(nodeV, nodeU)}.
*
* @since 23.0
*/
boolean hasEdgeConnecting(N nodeU, N nodeV);
/**
* Returns true if there is an edge that directly connects {@code endpoints} (in the order, if
* any, specified by {@code endpoints}). This is equivalent to {@code
* edges().contains(endpoints)}.
*
* <p>Unlike the other {@code EndpointPair}-accepting methods, this method does not throw if the
* endpoints are unordered; it simply returns false. This is for consistency with the behavior of
* {@link Collection#contains(Object)} (which does not generally throw if the object cannot be
* present in the collection), and the desire to have this method's behavior be compatible with
* {@code edges().contains(endpoints)}.
*
* @since 27.1
*/
boolean hasEdgeConnecting(EndpointPair<N> endpoints);
}
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