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How to write code for sparse array in java

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Release： 2023-04-19 08:22:02

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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:

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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

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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();
        }
    }
}

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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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