标签：BellmanFord weight get int 路径 edge edges vertexList
定义
贝尔曼-福特算法，可以从给定一个图和图中的源顶点src，找到从src到给定图中所有顶点的最短路径。该图可能包含负权重边。相对于Dijkstra算法的优势是可以处理负权重边，缺点则是复杂度高于Dijkstra 。具体算法的详细解析请参考https://www.geeksforgeeks.org/bellman-ford-algorithm-dp-23/，以下代码也是参考https://www.geeksforgeeks.org/bellman-ford-algorithm-dp-23/，只是根据自己的需要增加了一些东西。
package graph.bellman_ford;
import lombok.Data;
public class Graph {
private final int vertexCount;
private final int edgeCount;
private final Edge[] edge;
public Graph(int vertexCount, int edgeCount, Edge[] edge) {
this.vertexCount = vertexCount;
this.edgeCount = edgeCount;
this.edge = edge;
}
@Data
public static class Edge {
Vertex source;
Vertex destination;
int weight;
}
@Data
public static class Vertex {
int sequence;
String code;
String name;
}
public void bellmanFord(Graph graph, int src) {
int[] distance = new int[vertexCount];
for (int i = 0; i < vertexCount; ++i) {
distance[i] = Integer.MAX_VALUE;
}
distance[src] = 0;
for (int i = 1; i < vertexCount; ++i) {
for (int j = 0; j < edgeCount; ++j) {
int u = graph.edge[j].source.sequence;
int v = graph.edge[j].destination.sequence;
int weight = graph.edge[j].weight;
if (distance[u] != Integer.MAX_VALUE && distance[u] + weight < distance[v]) {
distance[v] = distance[u] + weight;
}
}
}
for (int j = 0; j < edgeCount; ++j) {
int u = graph.edge[j].source.sequence;
int v = graph.edge[j].destination.sequence;
int weight = graph.edge[j].weight;
if (distance[u] != Integer.MAX_VALUE && distance[u] + weight < distance[v]) {
return;
}
}
printArr(distance, vertexCount);
}
public void printArr(int[] distance, int vertexCount) {
for (int i = 0; i < vertexCount; ++i) {
System.out.println(i + "\t\t" + distance[i]);
}
}
}
测试
package graph.bellman_ford;
import java.util.ArrayList;
import java.util.List;
public class ShortestPathOfBellmanFord {
public static void main(String[] args) {
List<Graph.Vertex> vertexList = new ArrayList<>();
for (int i = 0; i < 5; i++) {
Graph.Vertex vertex = new Graph.Vertex();
vertex.code = "code" + i;
vertex.name = "name" + i;
vertex.sequence = i;
vertexList.add(vertex);
}
Graph.Edge[] edges = new Graph.Edge[8];
for (int i = 0; i < edges.length; i++) {
edges[i] = new Graph.Edge();
}
// edge 0 --> 1
edges[0].source = vertexList.get(0);
edges[0].destination = vertexList.get(1);
edges[0].weight = -1;
// edge 0 --> 2
edges[1].source = vertexList.get(0);
edges[1].destination = vertexList.get(2);
edges[1].weight = 4;
// edge 1 --> 2
edges[2].source = vertexList.get(1);
edges[2].destination = vertexList.get(2);
edges[2].weight = 3;
// edge 1 --> 3
edges[3].source = vertexList.get(1);
edges[3].destination = vertexList.get(3);
edges[3].weight = 2;
// edge 1 --> 4
edges[4].source = vertexList.get(1);
edges[4].destination = vertexList.get(4);
edges[4].weight = 2;
// edge 3 --> 2
edges[5].source = vertexList.get(3);
edges[5].destination = vertexList.get(2);
edges[5].weight = 5;
// edge 3 --> 1
edges[6].source = vertexList.get(3);
edges[6].destination = vertexList.get(1);
edges[6].weight = 1;
// edge 4--> 3
edges[7].source = vertexList.get(4);
edges[7].destination = vertexList.get(3);
edges[7].weight = -3;
Graph graph = new Graph(5, 8, edges);
graph.bellmanFord(graph, 0);
}
}
标签：BellmanFord,weight,get,int,路径,edge,edges,vertexList 来源： https://www.cnblogs.com/wkynf/p/15202669.html
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