《Java语言程序设计与数据结构》编程练习答案（第七章）（一）
英文名：Introduction to Java Programming and Data Structures, Comprehensive Version, 11th Edition
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7.1
import java.util.Scanner;
public class book {
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.print("Enter the number of students: ");
int num = input.nextInt();
int[] scores = new int[num];
int best = 0;
System.out.print("Enter "+num+" scores: ");
for(int i=0;i<num;i++)
{
scores[i]=input.nextInt();
if(scores[i]>best)
best=scores[i];
}
char[] grades={'A','B','C','D'};
for(int i=0;i<num;i++)
System.out.printf("Student %d score is %d and grade is %c\n",i,scores[i],scores[i]==best?'A':grades[(best-scores[i]-1)/10]);
}
}
7.2
import java.util.Scanner;
public class book {
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.print("Enter ten integers: ");
int[] nums = new int[10];
for(int i=0;i<10;i++)
nums[i]=input.nextInt();
for(int i=9;i>=0;i--)
System.out.print(nums[i]+" ");
}
}
7.3
import java.util.Scanner;
public class book {
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
int[] counts = new int[101];
for(int i=0;i<101;i++)
counts[i]=0;
System.out.print("Enter the integers between 1 and 100: ");
while(true)
{
int tmp=input.nextInt();
counts[tmp]++;
if(tmp==0)
break;
}
for(int i=1;i<=100;i++)
{
if(counts[i]!=0)
{
if(counts[i]>1)
System.out.printf("%d occurs %d times\n",i,counts[i]);
else
System.out.printf("%d occurs 1 time\n",i);
}
}
}
}
7.4
import java.util.Scanner;
public class book {
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
int[] occurs = new int[101];
int sum=0;
int count = 0;
while(true)
{
int tmp = input.nextInt();
if(tmp<0)
break;
occurs[tmp]++;
sum+=tmp;
count++;
}
double avg = 1.0*sum/count;
int lower = 0;
for(int i=0;i<avg;i++)
{
lower+=occurs[i];
}
System.out.println(lower+" students are lower than average.");
System.out.println((count-lower)+" students are not lower than average.");
}
}
7.5
import java.util.Scanner;
public class book {
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
int[] ass = new int[12];
int ptr = 0;
System.out.print("Enter 10 numbers: ");
for(int i=0;i<10;i++)
{
int tmp=input.nextInt();
boolean in = false;
for(int j=0;j<ptr;j++)
{
if(ass[j]==tmp)
{
in=true;
break;
}
}
if(!in)
{
ass[ptr]=tmp;
ptr++;
}
}
System.out.println("The number of distinct number is "+ptr);
System.out.print("The distinct numbers are: ");
for(int i=0;i<ptr;i++)
System.out.print(ass[i]+" ");
}
}
7.6
public class book {
public static void main(String[] args)
{
int[] ass =new int[60];
ass[0]=2;
int count=1;
while(true)
{
if(count==50)
break;
else{
int base = ass[count-1];
while(true)
{
base++;
if(isPrime(base,ass,count))
{
ass[count]=base;
count++;
break;
}
}
}
}
for(int i=0;i<count;i++)
System.out.print(ass[i]+" ");
}
public static boolean isPrime(int num,int[] dicks,int count)
{
boolean re = true;
for(int i=0;i<count;i++)
{
if(dicks[i]>Math.sqrt(num))
break;
if(num%dicks[i]==0)
{
re = false;
break;
}
}
return re;
}
}
7.7
public class book {
public static void main(String[] args)
{
int[] ass = new int[10];
for(int i=0;i<100;i++)
ass[(int)(Math.random()*10)]++;
for(int i=0;i<10;i++)
System.out.printf("%d occurs %d times\n",i,ass[i]);
}
}
7.8
import java.util.Scanner;
public class book {
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.print("Enter 10 doubles: ");
double[] ass = new double[10];
for(int i=0;i<10;i++)
ass[i]=input.nextDouble();
System.out.println("The average is "+average(ass));
}
public static int average(int[] array)
{
int sum = 0;
int len = array.length;
for (int value : array) sum += value;
return sum/len;
}
public static double average(double[] array)
{
double sum=0.0;
int len = array.length;
for(double ass : array) sum+=ass;
return sum/len;
}
}
7.9
import java.util.Scanner;
public class book {
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.print("Enter 10 doubles: ");
double[] ass = new double[10];
for(int i=0;i<10;i++)
ass[i]=input.nextDouble();
System.out.println("The minimum number is "+min(ass));
}
public static double min(double[] array)
{
double ss = array[0];
for (double v : array) {
if (v < ss)
ss = v;
}
return ss;
}
}
7.10
import java.util.Scanner;
public class book {
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.print("Enter 10 doubles: ");
double[] ass = new double[10];
for(int i=0;i<10;i++)
ass[i]=input.nextDouble();
System.out.println("The lowest index is "+indexOfSmallestElement(ass));
}
public static int indexOfSmallestElement(double[] array)
{
int ss = 0;
for(int i=0;i<array.length;i++)
{
if(array[i]<array[ss])
ss=i;
}
return ss;
}
}
7.11
import java.util.Scanner;
public class book {
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.print("Enter 10 doubles: ");
double[] ass = new double[10];
for(int i=0;i<10;i++)
ass[i]=input.nextDouble();
System.out.println("The mean is "+mean(ass));
System.out.println("The standard deviation is "+deviation(ass));
}
public static double deviation(double[] x)
{
double sum=0;
double mean=mean(x);
for(double v:x)sum+=Math.pow(v-mean,2);
return Math.sqrt(sum/(x.length-1));
}
public static double mean(double[] x)
{
double sum=0;
for (double v : x) sum += v;
return sum/x.length;
}
}
7.12
import java.util.Scanner;
public class book {
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.print("Enter 10 doubles: ");
double[] ass = new double[10];
for(int i=0;i<10;i++)
ass[i]=input.nextDouble();
reverse(ass);
for(double v:ass) System.out.print(v+" ");
}
public static double[] reverse(double[] ass)
{
int len = ass.length;
for(int i=0;i<len/2;i++)
{
double tmp = ass[i];
ass[i]=ass[len-i-1];
ass[len-i-1]=tmp;
}
return ass;
}
}
7.13
public class book {
public static void main(String[] args)
{
System.out.println("The random number is "+getRandom(1,1,4,5,1,4,1,9,1,9,8,1,0));
}
public static int getRandom(int... numbers)
{
int jb=(int)(Math.random()*54)+1;
while(inArray(numbers,jb))
jb=(int)(Math.random()*54)+1;
return jb;
}
public static boolean inArray (int[] ass,int dick)
{
for (int value : ass) {
if (value == dick)
return true;
}
return false;
}
}
