public class shuzu { public static void main(String[] agrs){ /** * Array-a collection of multiple data // one-dimensional array int a[]; int[] b; int arr[] = new int [5];//Dynamic assignment int[] arr1 =new int[]{1,2,3,4,5};//Static assignment //Array subscript starts from 0 System.out.println(arr.length ); System.out.println(arr1[1]); System.out.println(arr1[1*2]); System.out.println(arr[1]); //Two-dimensional array practice int[][ ] arr = new int[][]{ {3,8,2}, {2,7}, {9,0,1,6} };
int len = arr.length;
int res = 0;
for(int i = 0; i <len; i++){ int arr0[] = arr[i]; int llen = arr0.length; for(int j = 0; j <llen;j++){ res +=arr0[j]; } } System.out.println(res); */ /** * Common algorithms involved in arrays * 1. Find the maximum and minimum values of array elements , Sum, average int arr[] = new int[]{1,2,3,4,5,6,7,8 }; int max = arr[0]; int min = arr[0]; int sum = 0; int avg; int i; for( i = 0;i <arr.length;i++){
if(max <arr[i]){ max = arr[i]; } } System.out.println("Maximum:"+max); for(int j = 0; j <arr.length;j++){ if(min> arr[j]){ min = arr[j]; } } System.out.println("minimum value:"+min); //sum, average for(int k = 0;k <arr .length; k++){ sum +=arr[k]; } System.out.println("sum:"+sum); System.out.println("average:" + (sum / arr.length)); //2, the copy of the array int copy[] =new int[arr.length]; for(i = 0; i < arr.length;i++){
copy[i] = arr[i];
}
for(i = 0;i < copy.length;i++){
System.out.println(copy[i]);
}
System.out.println();
System.out.println();
//3、数组的反转
int temp[] = new int[arr.length];
int k =0;
for(i = arr.length - 1;i >= 0;i--){
//System.out.println(arr[i]);
temp[k] = arr[i];
k++;
}
arr = temp;
for(i = 0;i < arr.length;i++){
System.out.println(arr[i]);
}
*/
/**4、数组元素的排序
Bubbling method: sorting idea:
compare two adjacent elements, exchange if necessary, and arrange the largest element at the end every time the loop is completed (such as sorting from small to large), and the
next loop is to perform other numbers similarly Operation
int arr[] = new int[]{10,32,1,234,554,6,21};
int temp;
for(int i = 0;i <arr.length-1; i++){//Loop round
for( int j = 0; j <arr.length-1-i ;j++){//Every round, sort the array elements
if(arr[j]> arr[j + 1]){ temp = arr[j ]; arr[j] = arr[j + 1]; arr[j+ 1] = temp; } } } for(int i = 0;i <arr.length;i++){ System.out.println(arr[i ]); }*/ /**Array operation:
* (1) Create a class named TestArray and declare two variables array1 and array2 in the main() method. They are arrays of type int[].
(2) Use braces {} to initialize array1 to 8 prime numbers: 2,3,5,7,11,13,17,19.
(3) Display the content of array1.
(4) Assign the array2 variable equal to array1, modify the even index element in array2 to
make it equal to the index value (for example, array[0]=0, array[2]=2). Print out array1.
*/
int array1[] = new int[]{2,3,5,7,11,13,17,19};
int array2[]= new int[array1.length];
System.out.println("Print the value of array1: ");
for(int i = 0; i <array1.length;i++){
System.out.print( array1[i]+",");
}
System .out.println();
System.out.println();
//Assign array2 variable equal to array1
for(int i = 0; i <array1.length;i++){ array2[i] = array1[i]; } System .out.println("array2 array value:"); for(int i = 0; i <array2.length;i++){ System.out.print( array2[i]+","); } //4 , Modify the even index element in array2, //make it equal to the index value (such as array[0]=0,array[2]=2). Print out array1 for(int i = 0; i <array2.length;
if( i % 2 == 0){
array2[i] = i;
System.out.println(array2[i]);
}
else {
System.out.print(array2[i]+"\t");
}
}
System.out.println();
System.out.println();
//数组自身反转
int temp;
System.out.println("初始数组：");
for(int i = 0 ;i < array1.length;i++){
System.out.print(array1[i] + ",");
}
System.out.println();
System.out.println("数组自身反转:");
for(int i = array1.length - 1; i >= 0; i--){
System.out.print(array1[i] + ",");
}
}
}