How to write code for sparse array in java

Sparse organization

• When most of the elements in an array are 0, or are arrays of the same value, a sparse array can be used to save the array

• Sparse array, record how many rows and columns there are, how many different values ​​there are

• Record the elements and rows with different values ​​in a small size array, thus reducing the size of the program!

Let’s define the original array:

原始数组如下：
0 0 3 0 0 
0 0 0 0 4 
0 0 0 5 0 
0 0 6 0 0 
0 0 0 0 0

It can be seen that most of this array is 0, we can convert this array into a sparse array

The first row of the sparse array stores the total number of rows, the total number of columns and the total number of stored data.

//因为数组的下标是从0开始的，所以可以看出，第一行的第三个数，用下标表示，实际上是数组[0][2]
	5 5 4 
	0 2 3 
	1 4 4 
	2 3 5 
	3 2 6

Let’s take a look at how to implement this sparse array and how to restore the sparse array to

Code example:

package com.ling.array;
public class ArrayDemo11 {
    public static void main(String[] args) {
        int[][]   array=new int[5][5];
        array[0][2]=3;
        array[1][4]=4;
        array[2][3]=5;
        array[3][2]=6;
        System.out.println("原始数组如下：");
        for (int[] ints : array) {
            for (int anInt : ints) {
                System.out.print(anInt+" ");
            }
            System.out.println();
        }
        System.out.println("行"+"\t"+"列"+"\t"+"存放的数据"+"\t");
        //稀疏数组第一行存放的分别是总行数，总列数和存放的数据总数
//        System.out.println(5+"\t"+5+"\t"+4);
//        System.out.println(1+"\t"+3+"\t"+3);
//        System.out.println(2+"\t"+5+"\t"+4);
//        System.out.println(3+"\t"+4+"\t"+5);
//        System.out.println(4+"\t"+3+"\t"+6);
        int sum=0;
        for (int i = 0; i <5 ; i++) {
            for (int j = 0; j <5 ; j++) {
                if (array[i][j]!=0){
                    sum++;
                }
            }
        }
        int[][] arr2=new int[sum+1][3];
        //这个二维数组的第一行是确定的
        arr2[0][0]=5;
        arr2[0][1]=5;
        arr2[0][2]=sum;
        int count=0;
        for (int i = 0; i < array.length; i++) {
            for (int j = 0; j < array[i].length; j++) {
                if (array[i][j]!=0){
                    count++;
                    arr2[count][0]=i;
                    arr2[count][1]=j;
                    arr2[count][2]=array[i][j];
                }
            }
        }
        System.out.println("输出稀疏数组");
        for (int[] ints : arr2) {
            for (int anInt : ints) {
                System.out.print(anInt+" ");
            }
            System.out.println();
        }
    }
}

Output:

Output the original array
0 0 0 0 0 0 0 0 0 0 0
0 0 1 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 2 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
Number of valid values: 2
Output sparse array:
11 11 2
1 2 1
3 2 2
=========Divide========Cut========== Line =============
We can also restore the sparse array
Print the restored array
0 0 0 0 0 0 0 0 0 0 0
0 0 1 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 2 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0

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