1、图的定义。
图分为两个部分组长,包括边和点。将点用边连接起来就形成了图。
图也分为有向图与无向图。有向图就是边会带上方向。指明从哪个点到哪个点,反之无向图指没有方向得边。更多的时候会给边加上值,在图中,我们称之为该边得权。有向图中,叫做,有向带权图。无向图中,叫做,无向带权图。
2、图的构造
图是由边和点组成。那么构造就从边和点开始。
边:
每条边得两端各对应一个点,边得大小。所以图得边构造类如下:
/**
* 图中的边
*/
//边的左节点
GraphNode leftNode;
//边的右节点
GraphNode rightNode;
//边的权值
int value;
public GraphEdge(GraphNode leftNode,GraphNode rightNode,int value){
this.leftNode = leftNode;
this.rightNode = rightNode;
this.value = value;
}
点:
一个点可对应零条或者多条边。以及为了图得遍历,可对点设置boolean值。用来判断该点是否遍历过。点得构造类如下:
/**
* 图的节点
*/
int value;//节点得值
boolean tf;//节点是否遍历过
List<GraphEdge> edges;//该节点连接得边
public GraphNode(int value,boolean tf){
this.value = value;
this.tf = tf;
}
public void addEdge(GraphEdge edge){
if(edges == null){
edges= new ArrayList<>();
}
edges.add(edge);
}
3、图的遍历
遍历之前,先构造一个简单得图。构造代码如下:
/**
* 生成图
*/
//存放点得集合
List<GraphNode> nodeList = null;
//初始化点
public void initNode(int n ){
if(nodeList == null){
nodeList = new ArrayList<>();
}
GraphNode node = null;
for(int i = 0; i < n ; i++){
node = new GraphNode(i,false);
nodeList.add(node);
}
}
//初始化边
public void initGraph(int n){
initNode(n);
GraphEdge edge01 = new GraphEdge(nodeList.get(0),nodeList.get(1),0);
GraphEdge edge02 = new GraphEdge(nodeList.get(0),nodeList.get(2),0);
GraphEdge edge13 = new GraphEdge(nodeList.get(1),nodeList.get(3),0);
GraphEdge edge14 = new GraphEdge(nodeList.get(1),nodeList.get(4),0);
GraphEdge edge25 = new GraphEdge(nodeList.get(2),nodeList.get(5),0);
GraphEdge edge26 = new GraphEdge(nodeList.get(2),nodeList.get(6),0);
GraphEdge edge37 = new GraphEdge(nodeList.get(3),nodeList.get(7),0);
GraphEdge edge47 = new GraphEdge(nodeList.get(4),nodeList.get(7),0);
GraphEdge edge56 = new GraphEdge(nodeList.get(5),nodeList.get(6),0);
GraphEdge edge67 = new GraphEdge(nodeList.get(6),nodeList.get(7),0);
nodeList.get(0).addEdge(edge01);
nodeList.get(0).addEdge(edge02);
nodeList.get(1).addEdge(edge13);
nodeList.get(1).addEdge(edge14);
nodeList.get(2).addEdge(edge25);
nodeList.get(2).addEdge(edge26);
nodeList.get(3).addEdge(edge37);
nodeList.get(4).addEdge(edge47);
nodeList.get(5).addEdge(edge56);
nodeList.get(6).addEdge(edge67);
}
//获取所有点
public List<GraphNode> getNodeList() {
return nodeList;
}
构造完成之后进行图的遍历,可通过深度遍历与广度遍历完成
深度遍历可通过递归或栈完成。广度遍历可通过队列完成。
1、图得深度遍历-栈
public void dfSearchTraversing(GraphNode node) {
if (node == null) {
return;
}
Stack<GraphNode> stack = new Stack<GraphNode>();//创建栈
stack.push(node);//加入首节点
while (!stack.isEmpty()) {
GraphNode node1 = stack.pop();//弹出首节点
node1.setTf(true);//设置标记,该节点已访问
System.out.println("节点得值" + node1.getValue());
List<GraphEdge> list = node1.getEdges();//根据节点获得关联得边
if (list == null) {//该点无对应得边了
continue;
}
for (int i = 0; i < list.size(); i++) {
GraphEdge graphEdge = list.get(i);//获取每条边对应得另一端节点
GraphNode temp = graphEdge.getRightNode();
if (temp.getTf()) {//已访问过,就跳过该节点。
continue;
}
stack.push(temp);//将没访问过得节点加入栈中
}
}
}
2、图得深度遍历-递归
对递归算法不太了解得可参考上篇博客博客地址。
public void dfSearchTraversing(GraphNode node) {
if (node == null || node.getTf()) { //判断节点是否为空,或者是否已经遍历过
return;
}
node.setTf(true);//设置已遍历
System.out.println("节点:"+node.getValue());
List<GraphEdge> graphEdgeList = node.getEdges();//获取左节点的应得边
if(graphEdgeList == null){
return;
}
for(int i = 0; i < graphEdgeList.size(); i ++){
GraphNode graphNode = graphEdgeList.get(i).getRightNode();//获取边得右节点
if(graphNode.getTf()) {//判断是否已经遍历过
continue;
}
dfSearchTraversing(graphNode);//递归调用
}
}
3、图得广度遍历-队列
public void bfSearchTraversing(GraphNode node) {
if(node == null){
return;
}
Queue<GraphNode> queue = new LinkedList<>();//创建队列
queue.add(node);//加入第一个节点
while(queue.isEmpty() == false){
GraphNode node1 = queue.remove();//先进先出。移除节点
node1.setTf(true);//设置该节点已遍历过
System.out.println("值:"+node1.getValue());
List<GraphEdge> list = node1.getEdges();//获取点相关联得边
if(list == null){
continue;
}
for(int i = 0; i <list.size(); i++){
GraphEdge graphEdge = list.get(i);//获取边对应得右节点
GraphNode temp = graphEdge.getRightNode();
if(temp.getTf()){//判断该节点是否已经遍历过
continue;
}
queue.add(temp);//加入到队列中
}
}
}
个人记录,仅供参考。