/**
* 产生total个0-max的不重复随机数
* @param total
* @param max
*/
private int[] generateRam(int total, int max){
int[] arr = new int[total];
for (int i=0; i<total; i++)
{
arr[i] = (int)(Math.random()*(max+1));
for (int j = 0; j < i; j++){
if (arr[j] == arr[i]){
i--;
break;
}
}
}
for (int i = 0; i < total; i++)
System.out.print(arr[i] + " ");
return arr;
}
public class Test
{
// 产生20个0-30的不重复随机数
public static void main(String[] args)
{
int total = 20;
int max = 30;
int[] arr = new int[total];
for (int i=0; i<total; i++)
{
arr[i] = (int)(Math.random()*(max+1));
for (int j = 0; j < i; j++){
if (arr[j] == arr[i]){
i--;
break;
}
}
}
for (int i = 0; i < total; i++)
System.out.print(arr[i] + " ");
}
}
b.
Java code
import java.util.*;
public class Test
{
public static void main(String[] args)
{
int n=40;
int[] num = new int[n];
for(int i=0;i <num.length;i++)
num[i] = i+1;
int[] arr = new int[10];
for(int i=0;i <arr.length;i++)
{
int r =(int)(Math.random()*n);
arr[i]=num[r];
num[r]=num[n-1];
n--;
}
for(int i=0;i <arr.length;i++)
System.out.print(arr[i]+" ");
}
}
c.
Java code
import java.util.*;
public class Test
{
public static void main(String[] args)
{
LinkedList <Integer> myList= new LinkedList <Integer> ();
int n=40;
for(int i=0;i <n;i++)
myList.add(i+1);
int[] arr = new int[10];
for(int i=0;i <arr.length;i++)
{
arr[i]=myList.remove((int)(Math.random()*n));
n--;
}
for(int i=0;i <arr.length;i++)
{
System.out.print(arr[i]+" ");
}
}
}
d.
Java code
import java.util.*;
public class Test
{
public static void main(String[] args)
{
Set <Integer> mySet = new LinkedHashSet <Integer> ();
while(mySet.size() <10)
{
mySet.add((int)(Math.random()*40+1));
}
for(Integer i:mySet)
{
System.out.print(i+" ");
}
}
}
public class Test
{
public static void main(String[] args)
{
int[] arr = new int[10];
for (int i = 0; i < 10; i++)
{
arr[i] = (int) (Math.random() * 40) + 1;
for (int j = 0; j < i; j++)
{
if (arr[j] == arr[i])
{
i--;
break;
}
}
}
for (int i = 0; i < 10; i++)
System.out.print(arr[i] + " ");
}
}
b.
Java code
import java.util.*;
public class Test
{
public static void main(String[] args)
{
int n=40;
int[] num = new int[n];
for(int i=0;i <num.length;i++)
num[i] = i+1;
int[] arr = new int[10];
for(int i=0;i <arr.length;i++)
{
int r =(int)(Math.random()*n);
arr[i]=num[r];
num[r]=num[n-1];
n--;
}
for(int i=0;i <arr.length;i++)
System.out.print(arr[i]+" ");
}
}
c.
Java code
import java.util.*;
public class Test
{
public static void main(String[] args)
{
LinkedList <Integer> myList= new LinkedList <Integer> ();
int n=40;
for(int i=0;i <n;i++)
myList.add(i+1);
int[] arr = new int[10];
for(int i=0;i <arr.length;i++)
{
arr[i]=myList.remove((int)(Math.random()*n));
n--;
}
for(int i=0;i <arr.length;i++)
{
System.out.print(arr[i]+" ");
}
}
}
d.
Java code
import java.util.*;
public class Test
{
public static void main(String[] args)
{
Set <Integer> mySet = new LinkedHashSet <Integer> ();
while(mySet.size() <10)
{
mySet.add((int)(Math.random()*40+1));
}
for(Integer i:mySet)
{
System.out.print(i+" ");
}
}
}
Java代码
第一种方法，在一个待选数组中随机产生一个数，然后把他放到待选数组的最后，然后从length-1里随机产生下一个随机数，如此类推
public static int[] randoms()
{
Random r = new Random();
int temp1,temp2;
int send[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21};
int len = send.length;
int returnValue[] = new int[22];
for(int i=0;i<22;i++)
{
temp1 = Math.abs(r.nextInt())% len;
returnValue[i] = send[temp1];
temp2 = send[temp1];
send[temp1] = send[len-1];
send[len-1] = temp2;
len--;
}
return returnValue;
}
}
方法二：还是一个固定的无重复的数组，然后把这个数组随机调换位置，多次之后这个数组就是一个无重复的随机数组了。
public static int[] random2()
{
int send[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21};
int temp1,temp2,temp3;
Random r = new Random();
for(int i=0;i<send.length;i++) //随机交换send.length次
{
temp1 = Math.abs(r.nextInt())%(send.length-1); //随机产生一个位置
temp2 = Math.abs(r.nextInt())%(send.length-1); //随机产生另一个位置
if(temp1 != temp2)
{
temp3 = send[temp1];
send[temp1] = send[temp2];
send[temp2] = temp3;
}
}
return send;
}
