数据结构学习——图的邻接表（无向图，带权值有向图）

邻接表是数组与链表相结合的存储方法，相比于顺序存储结构（邻接矩阵），节省空间。
来个小例子（无向图）:
图1

图1邻接表的结构：

邻接表用链表来存储邻接点（分两个域，一个存顶点下标，一个存下一个邻接点的引用），通过一个类（我用了内部类，所以是private）定义邻接点：

private class AdgvexType {
        int verNum = -1;//存储顶点数组下标，默认零
        AdgvexType adg = null;//存储下一个邻接点的引用

        public int getVerNum() {
            return verNum;
        }

        public void setVerNum(int verNum) {
            this.verNum = verNum;
        }

        public int getWeightNum() {
            return weightNum;
        }

        public void setWeightNum(int weightNum) {
            this.weightNum = weightNum;
        }

        public AdgvexType getAdg() {
            return adg;
        }

        public void setAdg(AdgvexType adg) {
            this.adg = adg;
        }

        @Override
        public String toString() {
            return "AdgvexType [verNum=" + verNum + ", weightNum=" + weightNum
                    +  "]";
        }

    }

邻接表用数组存储图的顶点，数组中每个元素包含两个域（一个存顶点，一个存它第一个临界点的引用），定义顶点数组：

private VertexeType[] verArr;// 顶点数组

    // 顶点数据
    private class VertexeType {
        String vertexe = null;//存储顶点
        AdgvexType adg = null;//存储第一个邻接点的引用

        public VertexeType() {
        }

        public VertexeType(String vertexe) {
            this.vertexe = vertexe;
        }

        public String getVertexe() {
            return vertexe;
        }

        public void setVertexe(String vertexe) {
            this.vertexe = vertexe;
        }

        public AdgvexType getAdg() {
            return adg;
        }

        public void setAdg(AdgvexType adg) {
            this.adg = adg;
        }

        @Override
        public String toString() {
            return "VertexeType [vertexe=" + vertexe + ", adg=" + adg + "]";
        }

    }

再说说带权值的有向图（在原来的基础上）：
图2
需要多记录一项属性（权值），对邻接点类型加一个域，来存储权值，结构如下：

对class AdgvexType类加一条属性（成员变量）即可：

int weightNum = 0;

通过构造方法为顶点数组赋值：

    public AdjacencyList(String[] arr) {
        this.MAXVEX = arr.length;
        this.verArr = new VertexeType[this.MAXVEX];
        for (int i = 0; i < arr.length; i++) {
            this.verArr[i] = new VertexeType(arr[i]);
        }
    }

通过二维数组添加所有邻接点：

    public void addAdg(String[][] arr) {
        for (int i = 0; i < arr.length; i++) {
            AdgvexType temp = null;
            int[] pos = this.getPosition(arr[i]);
            AdgvexType adg = new AdgvexType();
            adg.setWeightNum(Integer.valueOf( arr[i][2]));//设置权值
            adg.setVerNum(pos[1]);
            temp = this.verArr[pos[0]].getAdg();
            if (temp == null) {
                this.verArr[pos[0]].setAdg(adg);
                continue;
            }
            while (true) {
                if (temp.getAdg() != null) {
                    temp = temp.getAdg();
                } else {
                    temp.setAdg(adg);
                    break;
                }
            }
        }

    }
    //查找顶点位置
    private int[] getPosition(String[] arr) {
        int[] arrInt = new int[2];
        for (int i = 0; i < this.MAXVEX; i++) {
            if (this.verArr[i].getVertexe().equals(arr[0])) {
                arrInt[0] = i;
                break;
            }
        }
        for (int i = 0; i < this.MAXVEX; i++) {
            if (this.verArr[i].getVertexe().equals(arr[1])) {
                arrInt[1] = i;
                break;
            }
        }
        return arrInt;
    }

测试代码：

package com.nuc.Graph;

public class TestAdg {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        // TODO Auto-generated method stub
                String[] str={"v0","v1","v2","v3"};
                AdjacencyList adj=new AdjacencyList(str);
                String[][] edges=new String[][]{
                        {"v0","v3","5"},//顶点，顶点，权值
                        {"v1","v0","1"},
                        {"v1","v2","3"},
                        {"v2","v0","7"},
                        {"v2","v1","4"}
                };
                adj.addAdg(edges);
                adj.show();
    }

}

下边是完整代码：

import java.util.Arrays;

public class AdjacencyList {
    private int MAXVEX;// 顶点数组长度
    private VertexeType[] verArr;// 顶点数组

    // 顶点数据
    private class VertexeType {
        String vertexe = null;
        AdgvexType adg = null;

        public VertexeType() {
        }

        public VertexeType(String vertexe) {
            this.vertexe = vertexe;
        }

        public String getVertexe() {
            return vertexe;
        }

        public void setVertexe(String vertexe) {
            this.vertexe = vertexe;
        }

        public AdgvexType getAdg() {
            return adg;
        }

        public void setAdg(AdgvexType adg) {
            this.adg = adg;
        }

        @Override
        public String toString() {
            return "VertexeType [vertexe=" + vertexe + ", adg=" + adg + "]";
        }

    }

    // 边表节点
    private class AdgvexType {
        int verNum = -1;
        int weightNum = 0;
        AdgvexType adg = null;

        public int getVerNum() {
            return verNum;
        }

        public void setVerNum(int verNum) {
            this.verNum = verNum;
        }

        public int getWeightNum() {
            return weightNum;
        }

        public void setWeightNum(int weightNum) {
            this.weightNum = weightNum;
        }

        public AdgvexType getAdg() {
            return adg;
        }

        public void setAdg(AdgvexType adg) {
            this.adg = adg;
        }

        @Override
        public String toString() {
            return "AdgvexType [verNum=" + verNum + ", weightNum=" + weightNum
                    +  "]";
        }

    }

    // 初始化，为顶点数组赋值
    public AdjacencyList(String[] arr) {
        this.MAXVEX = arr.length;
        this.verArr = new VertexeType[this.MAXVEX];
        for (int i = 0; i < arr.length; i++) {
            this.verArr[i] = new VertexeType(arr[i]);
        }
    }

    public void addAdg(String[][] arr) {
        for (int i = 0; i < arr.length; i++) {
            AdgvexType temp = null;
            int[] pos = this.getPosition(arr[i]);
            AdgvexType adg = new AdgvexType();
            adg.setVerNum(pos[1]);
            temp = this.verArr[pos[0]].getAdg();
            if (temp == null) {
                this.verArr[pos[0]].setAdg(adg);
                continue;
            }
            while (true) {
                if (temp.getAdg() != null) {
                    temp = temp.getAdg();
                } else {
                    temp.setAdg(adg);
                    break;
                }
            }
        }

    }

    private int[] getPosition(String[] arr) {
        int[] arrInt = new int[2];
        for (int i = 0; i < this.MAXVEX; i++) {
            if (this.verArr[i].getVertexe().equals(arr[0])) {
                arrInt[0] = i;
                break;
            }
        }
        for (int i = 0; i < this.MAXVEX; i++) {
            if (this.verArr[i].getVertexe().equals(arr[1])) {
                arrInt[1] = i;
                break;
            }
        }
        return arrInt;
    }

    public void show() {
        for (VertexeType v : verArr) {
            if (v.getAdg() == null) {
                System.out.println(v);
                continue;
            }
            AdgvexType temp = v.getAdg();
            String s = v + "-->" + temp;
            while (true) {
                if (temp.getAdg() != null) {
                    temp = temp.getAdg();
                    s +="-->"+ temp;
                } else {
                    System.out.println(s);
                    break;
                }
            }
        }
    }

}