二十四点

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import java.util.ArrayList;import java.util.HashSet;import java.util.List;import java.util.Random;import java.util.Set;import java.util.Scanner;public class Count24 {    private List<String> answerList=new ArrayList<String>();    public List<String> getAnswerList() {        return answerList;    }    public static class Data{        public float[]  arr;        public String expStr="";        public String[] strs;        public Data(){}        public Data(int a,int b,int c,int d) {            arr=new float[]{a,b,c,d};            strs=new String[]{a+"",b+"",c+"",d+""};            expStr=a+"";        }        public Data(int arr[]) {            this.arr=new float[]{arr[0],arr[1],arr[2],arr[3]};            this.strs=new String[]{arr[0]+"",arr[1]+"",arr[2]+"",arr[3]+""};        }    }    public void count(Data data){        float[] arr=data.arr;        if(arr.length<=1){            if(arr.length==1&&arr[0]==24){                answerList.add(data.expStr.substring(1, data.expStr.length()-1));            }            return ;        }        for(int i=0,len=arr.length;i<len-1; i++){            for(int j=i+1;j<len;j++){                float x=arr[i];                float y=arr[j];                String xs=data.strs[i];                String ys=data.strs[j];                for(int k=0;k<6;k++){                    Data newData=getNewArr(data,i);                    switch(k){                        case 0:                        newData.arr[j-1]=x+y;                            newData.expStr=xs+"+"+ys;                        break;                        case 1:                        newData.arr[j-1]=x-y;                            newData.expStr=xs+"-"+ys;                        break;                        case 2:                        newData.arr[j-1]=y-x;                        newData.expStr=ys+"-"+xs;                        break;                        case 3:                        newData.arr[j-1]=x*y;                            newData.expStr=xs+"*"+ys;                        break;                        case 4:                        if(y!=0){                            newData.arr[j-1]=x/y;                                newData.expStr=xs+"/"+ys;                        }else {                            continue;                        }                        break;                        case 5:                        if(x!=0){                            newData.arr[j-1]=y/x;                                newData.expStr=ys+"/"+xs;                        }else {                            continue;                        }                        break;                    }                    newData.expStr="("+newData.expStr+")";                    newData.strs[j-1]=newData.expStr;                    count(newData);                }            }        }            }    private static Data getNewArr(Data data, int i) {        Data newData=new Data();        newData.expStr=data.expStr;        newData.arr=new float[data.arr.length-1];        newData.strs=new String[data.arr.length-1];        for(int m=0,len=data.arr.length,n=0;m<len;m++){            if(m!=i){                newData.arr[n]=data.arr[m];                newData.strs[n]=data.strs[m];                n++;            }        }        return newData;    }        public static final List<String> easyCount(int[] curRandNums){        Count24 count24=new Count24();        count24.count(new Data(curRandNums));        Set<String> set=new HashSet<String>(count24.getAnswerList());        return new ArrayList<String>(set);    }        public static void main(String[] args) throws InterruptedException {        long start=System.currentTimeMillis();        Scanner in=new Scanner(System.in);        System.out.println("Please input four counts:");        int a=in.nextInt();        int b=in.nextInt();        int c=in.nextInt();        int d=in.nextInt();        if(a>0 && b>0 && c>0 && d>0 && a<14 && b<14 && c<14 && d<14  ){        List<String> answerStris=easyCount(new int[]{a,b,c,d});        for (String string : answerStris) {        System.out.println(string);        }        }        else System.out.println("Error!");    }}
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