Java程序设计第五章课后题

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<pre class="blockcode"><code class="language-java">import java.util.Scanner;
class Demo05_01_02{
public static void main(String[] args){
 int[] arr=new int[101];
 Scanner scanner=new Scanner(System.in);
 System.out.print("Enter numbers:");
 while(true){
 int num=scanner.nextInt();
 if(num==0){
 break;
 }
 arr[num]++;
 }
 for(int i=0;i<arr.length;i++){
 if(arr[i]!=0){
 System.out.println(i+" occurs "+arr[i]+(arr[i]>1?" times":" time"));
 }
 }
}
}</code></pre>
 
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<pre class="blockcode"><code class="language-java">import java.util.*;
class Demo05_02{
public static void main(String[] args){
 /*
 思路1
 在全部输入之后去重复 func1
 思路2
 边输入边去重复 func2
 */
 // func1();
 func2();
}
public static void func2(){
 int[] arr=new int[0];
 Scanner scanner = new Scanner(System.in);
 System.out.print("Enter numbers:");
 for(int i=0;i<10;i++){
 int num=scanner.nextInt();
 if(!contains(arr,num)){
 arr=copyOf(arr,arr.length+1);
 arr[arr.length-1]=num;
 }
 }
 System.out.println(Arrays.toString(arr));
}
public static void func1(){
 //1.循环遍历数组进行赋值
 Scanner scanner = new Scanner(System.in);
 System.out.print("Enter numbers:");
 int[] arr = new int[10];
 for(int i = 0;i < arr.length;i++){
 arr[i] = scanner.nextInt();
 }
 //2.开始对已有的数据进行去重复操作
 // 1 2 3 3 2 4 3 2 4 1
 // 1 2 3 4
 // method1(arr); //空间S(n) 时间O(nm)
 // method2(arr); //空间S(1) 时间O(n^2)
 // method3(arr);
}
public static void method3(int[] arr){
 //不创建额外空间不许改变原先的顺序
 int i=0;
 int size=arr.length;
 while(i<size){
 for(int j=i+1;j<size;){
 if(arr[j]==arr[i]){
 for(int k=j+1;k<size;k++){
 arr[k-1]=arr[k];
 }
 size--;
 }else{
 j++;
 }
 }
 i++;
 }
 for(i=0;i<size;i++){
 System.out.print(arr[i]+" ");
 }
}
public static void method2(int[] arr){
 //插入排序
 for(int i=1;i<arr.length;i++){
 int e=arr[i];
 int j;
 for(j=i;j>0&&arr[j-1]>e;j--){
 arr[j]=arr[j-1];
 }
 arr[j]=e;
 }
 //连续相等
 for(int i=0;i<arr.length;){ //O(n)
 System.out.print(arr[i]+" ");
 int count=1;
 for(int j=i+1;j<arr.length;j++){
 if(arr[j]==arr[i]){
 count++;
 }else{
 break;
 }
 }
 i+=count;
 }
}
public static void method1(int[] arr){
 int[] newArr=new int[0];
 for(int i=0;i<arr.length;i++){ //O(n)
 if(!contains(newArr,arr[i])){ //O(m)
 newArr=copyOf(newArr,newArr.length+1);
 newArr[newArr.length-1]=arr[i];
 }
 }
 System.out.println(Arrays.toString(newArr));
}
public static boolean contains(int[] arr,int key){
 for(int i=0;i<arr.length;i++){
 if(arr[i]==key){
 return true;
 }
 }
 return false;
}
public static int[] copyOf(int[] arr,int newLen){
 int[] newArr=new int[newLen];
 for(int i=0;i<arr.length;i++){
 newArr[i]=arr[i];
 }
 return newArr;
}

}</code></pre>
5.3 
 
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<pre class="blockcode"><code class="language-java">import java.util.*;
class Demo05_03{
public static void main(String[] args){
 //1.获取用户的输入只不过第一个输入的数据时数据的个数(数组的长度)
 Scanner scanner=new Scanner(System.in);
 System.out.print("Enter a list:");
 int len=scanner.nextInt();//获取的第一个数值就是数组的长度
 int[] arr=new int[len];
 for(int i=0;i<arr.length;i++){
 arr[i]=scanner.nextInt();
 }
 //2.对数组进行有序的判断
 if(isSorted(arr)){
 System.out.println("The list is already sorted.");
 }else{