The concept and usage of Java two-dimensional arrays

Two-dimensional arrays

An array of arrays---each element of a two-dimensional array is a one-dimensional array

Defining formats

data type [] Array name = new data type [length of two-dimensional array/number of one-dimensional array included] [length of each one-dimensional array];

int[][] arr = new INT[3][5];---defines a two-dimensional array of integers that contains 3 one-dimensional arrays, each one-dimensional array can store 5 integers

ARR[0]---a one-dimensional array at a location labeled 0

ARR[1][3]---If you want to get a specific element requires two subscript

data type [] Array name = new data type [length of two-dimensional array/number of contained one-dimensional array] [];

int[][] arr = new int[3][];----represents a two-dimensional array of one-dimensional arrays that contain three integers (-------------this sentence is well understood------------------------)

data type [] Array name = {{element},{element 1, Element 2},......};

Int[][] arr = {{2,5},{1},{3,2,4},{1,7,5,9}};

Note: [] before the variable name, it is the data type, and if [] after that, it belongs to the current variable name.

Application of two-dimensional array

Length of two-dimensional array: array name. length---each one-dimensional array: array name [subscript].length

Two-dimensional array traversal---dual for loop

For (// traversal of a two-dimensional array, each element traversed is a one-dimensional array for (// traversal of a one-dimensional array at the corresponding location system.  out. println (Arr[i][j]);}}      

Inversion of two-dimensional arrays---kinsoku

for (0, end = arr.length-1; start < end; start++,end--) {int[] temp = Arr[start];arr[start] =
          
            Arr[end];arr[end] =
            temp;} 
              

Enter the number of rows from the console to print the corresponding Yang Hui triangle

//Get the number of rows from the console scanner s =New Scanner (System.Inch);int row =S.nextint ();//A two-dimensional array is defined according to the number of rows, because the number of elements in each row is different, so the number of each row is undefinedint[][] arr =NewInt[Row] [];//Traversing a two-dimensional arrayForint i =0; i < row; i++){//Initialize this one-dimensional array of each row arr[i] =NewInt[i +1];//Iterate through this one-dimensional array and add elementsForInt J =0; J <= I; J + +){// The beginning and ending elements of each column are 1, at the beginning, j=0, at the end, j=i if (j = = 0 | | J == i) {Arr[i][j] = 1;} else {// Each element is the sum of the elements of its previous line and the diagonal elements arr[i][j] = arr[i-1][j] + arr[i-1][ J-1];} System. out.print (Arr[i][j] +  "\t  ");} System. out.println ();}       

Results:

1

1 1

1 2 1

1 3 3 1

1 4 6) 4 1

1 5 10 10 5 1

Yang Hui triangle with a two-dimensional array of understanding:

ARR[I][J] = Arr[i-1][j] + arr[i-1][j-1]

The concept and usage of Java two-dimensional arrays