java实现遗传算法实例分享(打印城市信息)

import java.util.*;
public class tsp { 
    private string cityname[]={"北京","上海","天津","重庆","哈尔滨","长春","沈阳","呼和浩特","石家庄","太原","济南","郑州","西安","兰州","银川","西宁","乌鲁木齐","合肥","南京","杭州","长沙","南昌","武汉","成都","贵州","福建","台北","广州","海口","南宁","昆明","拉萨","香港","澳门"};
    //private string cityend[]=new string[34];
    private int citynum=cityname.length;     //城市个数
    private int popsize = 50;               //种群数量
    private int maxgens = 20000;            //迭代次数
    private double pxover = 0.8;            //交叉概率
    private double pmultation = 0.05;       //变异概率
    private long[][] distance = new long[citynum][citynum];
    private int range = 2000;               //用于判断何时停止的数组区间
    private class genotype {
        int city[] = new int[citynum];      //单个基因的城市序列
        long fitness;                      //该基因的适应度
        double selectp;                        //选择概率
        double exceptp;                        //期望概率
        int isselected;                        //是否被选择
    }
    private genotype[] citys = new genotype[popsize];
    /**
     *    构造函数，初始化种群
     */
    public tsp() {
        for (int i = 0; i < popsize; i++) {
            citys[i] = new genotype();
            int[] num = new int[citynum];
            for (int j = 0; j < citynum; j++)
                num[j] = j;
            int temp = citynum;
            for (int j = 0; j < citynum; j++) {
                int r = (int) (math.random() * temp);
                citys[i].city[j] = num[r];
                num[r] = num[temp - 1];
                temp--;
            }
            citys[i].fitness = 0;
            citys[i].selectp = 0;
            citys[i].exceptp = 0;
            citys[i].isselected = 0;
        }
        initdistance();
    }
    /**
     *  计算每个种群每个基因个体的适应度，选择概率，期望概率，和是否被选择。
     */
    public void calall(){
        for( int i = 0; i< popsize; i++){
            citys[i].fitness = 0;
            citys[i].selectp = 0;
            citys[i].exceptp = 0;
            citys[i].isselected = 0;
        }
        calfitness();
        calselectp();
        calexceptp();
        calisselected();
    }
    /**
     *    填充，将多选的填充到未选的个体当中
     */
    public void pad(){
        int best = 0;
        int bad = 0;
        while(true){          
            while(citys[best].isselected <= 1 && best<popsize-1)
                best ++;
            while(citys[bad].isselected != 0 && bad<popsize-1)
                bad ++;
            for(int i = 0; i< citynum; i++)
                citys[bad].city[i] = citys[best].city[i];
                citys[best].isselected --;
                citys[bad].isselected ++;
                bad ++;  
            if(best == popsize ||bad == popsize)
                break;
        }
    }
    /**
     *    交叉主体函数
     */
    public void crossover() {
        int x;
        int y;
        int pop = (int)(popsize* pxover /2);
        while(pop>0){
            x = (int)(math.random()*popsize);
            y = (int)(math.random()*popsize);
            executecrossover(x,y);//x y 两个体执行交叉
            pop--;
        }
    }
    /**
     * 执行交叉函数
     * @param 个体x
     * @param 个体y
     * 对个体x和个体y执行佳点集的交叉，从而产生下一代城市序列
     */
    private void executecrossover(int x,int y){
        int dimension = 0;
        for( int i = 0 ;i < citynum; i++)
            if(citys[x].city[i] != citys[y].city[i]){
                dimension ++;
            } 
        int diffitem = 0;
        double[] diff = new double[dimension];
        for( int i = 0 ;i < citynum; i++){
            if(citys[x].city[i] != citys[y].city[i]){
                diff[diffitem] = citys[x].city[i];
                citys[x].city[i] = -1;
                citys[y].city[i] = -1;
                diffitem ++;
            } 
        }
        arrays.sort(diff);
        double[] temp = new double[dimension];
        temp = gp(x, dimension);
        for( int k = 0; k< dimension;k++)
            for( int j = 0; j< dimension; j++)
                if(temp[j] == k){
                    double item = temp[k];
                    temp[k] = temp[j];
                    temp[j] = item;
                    item = diff[k];
                    diff[k] = diff[j];
                    diff[j] = item; 
                }
        int tempdimension = dimension;
        int tempi = 0;
        while(tempdimension> 0 ){
            if(citys[x].city[tempi] == -1){
                citys[x].city[tempi] = (int)diff[dimension - tempdimension];
                tempdimension --;
            } 
            tempi ++;
        }
        arrays.sort(diff);
        temp = gp(y, dimension);
        for( int k = 0; k< dimension;k++)
            for( int j = 0; j< dimension; j++)
                if(temp[j] == k){
                    double item = temp[k];
                    temp[k] = temp[j];
                    temp[j] = item;
                    item = diff[k];
                    diff[k] = diff[j];
                    diff[j] = item; 
                }
        tempdimension = dimension;
        tempi = 0;
        while(tempdimension> 0 ){
            if(citys[y].city[tempi] == -1){
                citys[y].city[tempi] = (int)diff[dimension - tempdimension];
                tempdimension --;
            } 
            tempi ++;
        }
    }
    /**
     * @param individual 个体
     * @param dimension    维数
     * @return 佳点集   (用于交叉函数的交叉点）    在executecrossover()函数中使用
     */
    private double[] gp(int individual, int dimension){
        double[] temp = new double[dimension];
        double[] temp1 = new double[dimension];
        int p = 2 * dimension + 3;
        while(!issushu(p))
            p++;
        for( int i = 0; i< dimension; i++){
            temp[i] = 2*math.cos(2*math.pi*(i+1)/p) * (individual+1);
            temp[i] = temp[i] - (int)temp[i];
            if( temp [i]< 0)
                temp[i] = 1+temp[i];
        }
        for( int i = 0; i< dimension; i++)
            temp1[i] = temp[i];
        arrays.sort(temp1);
        //排序
        for( int i = 0; i< dimension; i++)
            for( int j = 0; j< dimension; j++)
                if(temp[j]==temp1[i])
                    temp[j] = i;
        return temp;
    }
    /**
     *    变异
     */
    public void mutate(){
        double random;
        int temp;
        int temp1;
        int temp2;
        for( int i = 0 ; i< popsize; i++){
            random = math.random();
            if(random<=pmultation){
                temp1 = (int)(math.random() * (citynum));
                temp2 = (int)(math.random() * (citynum));
                temp = citys[i].city[temp1];
                citys[i].city[temp1] = citys[i].city[temp2];
                citys[i].city[temp2] = temp;
            }
        }     
    }
    /**
     * 打印当前代数的所有城市序列，以及其相关的参数
     */
    public void print(){
    /**
     * 初始化各城市之间的距离
     */
    private void initdistance(){
        for (int i = 0; i < citynum; i++) {
            for (int j = 0; j < citynum; j++){
                distance[i][j] = math.abs(i-j);
            }
        }
    }
    /**
     * 计算所有城市序列的适应度
     */
    private void calfitness() {
        for (int i = 0; i < popsize; i++) {
            for (int j = 0; j < citynum - 1; j++)
                citys[i].fitness += distance[citys[i].city[j]][citys[i].city[j + 1]];
            citys[i].fitness += distance[citys[i].city[0]][citys[i].city[citynum - 1]];
        }
    }
    /**
     * 计算选择概率
     */
    private void calselectp(){
        long sum = 0;
        for( int i = 0; i< popsize; i++)
            sum += citys[i].fitness;
        for( int i = 0; i< popsize; i++)
            citys[i].selectp = (double)citys[i].fitness/sum;
    }
    /**
     * 计算期望概率
     */
    private void calexceptp(){
        for( int i = 0; i< popsize; i++)
            citys[i].exceptp = (double)citys[i].selectp * popsize;
    }
    /**
     * 计算该城市序列是否较优，较优则被选择，进入下一代
     */
    private void calisselected(){
        int needselecte = popsize;
        for( int i = 0; i< popsize; i++)
            if( citys[i].exceptp<1){
                citys[i].isselected++;
                needselecte --;
            }
        double[] temp = new double[popsize];
        for (int i = 0; i < popsize; i++) {
//          temp[i] = citys[i].exceptp - (int) citys[i].exceptp;
//          temp[i] *= 10;
            temp[i] = citys[i].exceptp*10;
        }
        int j = 0;
        while (needselecte != 0) {
            for (int i = 0; i < popsize; i++) {
                if ((int) temp[i] == j) {
                    citys[i].isselected++;
                    needselecte--;
                    if (needselecte == 0)
                        break;
                }
            }
            j++;
        }
    }
    /**
     * @param x
     * @return 判断一个数是否是素数的函数
     */
    private boolean issushu( int x){
           if(x<2) return false;
           for(int i=2;i<=x/2;i++)
           if(x%i==0&&x!=2) return false;
           return true;
        }
    /**
     * @param x 数组
     * @return x数组的值是否全部相等，相等则表示x.length代的最优结果相同，则算法结束
     */
    private boolean issame(long[] x){
        for( int i = 0; i< x.length -1; i++)
            if(x[i] !=x[i+1])
                return false;
        return true;
    }
    /**
     * 打印任意代最优的路径序列
     */
    private void printbestroute(){
        calall();
        long temp = citys[0].fitness;
        int index = 0;
        for (int i = 1; i < popsize; i++) {
            if(citys[i].fitness<temp){
                temp = citys[i].fitness;
                index = i;
            }
        }
        system.out.println();
        system.out.println("最佳路径的序列：");
        for (int j = 0; j < citynum; j++)
        {
            string cityend[]={cityname[citys[index].city[j]]};
            for(int m=0;m<cityend.length;m++)
            {
                system.out.print(cityend[m] + " ");
            }
        }
            //system.out.print(citys[index].city[j] + cityname[citys[index].city[j]] + "  ");
            //system.out.print(cityname[citys[index].city[j]]);
        system.out.println();
    }
    /**
     * 算法执行
     */
    public void run(){
        long[] result = new long[range];
        //result初始化为所有的数字都不相等
        for( int i  = 0; i< range; i++)
            result[i] = i;
        int index = 0;       //数组中的位置
        int num = 1;     //第num代
        while(maxgens>0){
            system.out.println("-----------------  第  "+num+" 代  -------------------------");
            calall();
            print();
            pad();
            crossover();
            mutate();
            maxgens --;
            long temp = citys[0].fitness;
            for ( int i = 1; i< popsize; i++)
                if(citys[i].fitness<temp){
                    temp = citys[i].fitness;
                }
            system.out.println("最优的解："+temp);
            result[index] = temp;
            if(issame(result))
                break;
            index++;
            if(index==range)
                index = 0;
            num++;
        }
        printbestroute();
    }
    /**
     * @param a 开始时间
     * @param b   结束时间
     */
    public void caltime(calendar a,calendar b){
        long x = b.gettimeinmillis() - a.gettimeinmillis();
        long y = x/1000;
        x = x - 1000*y;
        system.out.println("算法执行时间："+y+"."+x+" 秒");
    }
    /**
     *    程序入口
     */
    public static void main(string[] args) {
        calendar a = calendar.getinstance(); //开始时间
        tsp tsp = new tsp();
        tsp.run();
        calendar b = calendar.getinstance(); //结束时间
        tsp.caltime(a, b);
    }
}