Basic introduction

Most of the elements in an array are 0 when , Or for the same value , You can use a sparse array to hold the array . This can save space , Increase of efficiency .

processing method

• Record the number of rows and columns in a two-dimensional array , How many different values
• Record rows and columns and values of elements with different values in a small array , To reduce the size of the program .

Realize the idea

Two dimensional array To Sparse array :

• Traverse the original two-dimensional array , Get the blame 0 Number count
• Building sparse arrays sparseArr[count+][3]
• Two dimensional array is not 0 Elements are stored in sparse arrays

Sparse array To a two-dimensional array

• Read the first line of the sparse array , Build the original two-dimensional array
• Traversing the remaining elements of a sparse array , Fill in a two-dimensional array

public class SparseArray {

public static void main(String[] args) {

// Create an original two-dimensional array [11][11]
//0: No chess pieces , 1: The spots 2: Blueberry 
int[][] arr = new int[11][11];
arr[1][2] = 1;
arr[2][3] = 2;
for (int[] row : arr) {

for (int item : row) {

System.out.printf("%d\t", item);
}
System.out.println();
}
// Traversing a two-dimensional array , Get the blame 0 Number of data 
int count = 0;
for (int i = 0; i < arr.length; i++) {

for (int j = 0; j < arr[i].length; j++) {

if (arr[i][j] != 0) {

count++;
}
}
}
// Create the corresponding sparse array 
int[][] sparseArr = new int[count + 1][3];
// Assign values to sparse arrays 
sparseArr[0][0] = arr.length;
sparseArr[0][1] = arr[0].length;
sparseArr[0][2] = count;
// Traversing a two-dimensional array , Will not 0 Values are stored in a sparse array 
// Record the number one 0 Elements 
int k = 0;
for (int i = 0; i < arr.length; i++) {

for (int j = 0; j < arr[i].length; j++) {

if (arr[i][j] != 0) {

k++;
sparseArr[k][0] = i;
sparseArr[k][1] = j;
sparseArr[k][2] = arr[i][j];
}
}
}
System.out.println(" Two dimensional array to sparse array :");
for (int i = 0; i < sparseArr.length; i++) {

System.out.printf("%d\t%d\t%d\t\n", sparseArr[i][0], sparseArr[i][1], sparseArr[i][2]);
}
System.out.println(" Sparse array to two-dimensional array :");
// Read the first line of the sparse array , And build the original two-dimensional array 
int row = sparseArr[0][0];
int col = sparseArr[0][1];
int[][] arr2 = new int[row][col];
// Read the last few lines of sparse array data , And assign it to the original array 
for (int i = 1; i < sparseArr.length; i++) {

arr2[sparseArr[i][0]][sparseArr[i][1]] = sparseArr[i][2];
}
for (int[] row2 : arr2) {

for (int item : row2) {

System.out.printf("%d\t", item);
}
System.out.println();
}
}
}