How to define and use java sparse array

Features

1. It can compress data and reduce the use of memory space.

Process

2. Record the coordinates and values ​​of the array elements.

3. The sparse array has 3 columns, namely rows, columns, and values. The number of rows is the number of different values ​​in the original array plus 1;

array[0] records a set of row numbers and The number of columns, and the number of different values;

Then each row records a value and marks its own value under the rows and columns of the original array.

Example

public static void main(String[] args) {
    //创建一个原始的二维数组
    //0：没有棋子，1：黑子，2：白子
    int chessArr1[][] = new int[11][11];
    //下面先固定二维数组的元素，后面可优化~
    chessArr1[1][2] = 1;
    chessArr1[2][3] = 2;
    chessArr1[4][5] = 2;
    //输出原始的二维数组：
    System.out.println("原始的二维数组：");
    printArray(chessArr1);
 
    //下面将二维数组转化为稀疏数组
    //1.先遍历二维数组，得到非0数据的个数
    int sum = 0;
 
    for (int i = 0; i < 11; i++) {
        for (int j = 0; j < 11; j++) {
            if (chessArr1[i][j] != 0) {
                sum++;
            }
        }
    }
 
    //2.创建对应的稀疏数组
    int sparesArr[][] = new int[sum + 1][3];
    //给稀疏数组赋值
    sparesArr[0][0] = 11;
    sparesArr[0][1] = 11;
    sparesArr[0][2] = sum;
 
    //遍历二维数组，将非0的值存放在sparesArr中
    int count = 0;//count 用于记录是第几个非0数据
    for (int i = 0; i < 11; i++) {
        for (int j = 0; j < 11; j++) {
            if (chessArr1[i][j] != 0) {
                count++;
                sparesArr[count][0] = i;
                sparesArr[count][1] = j;
                sparesArr[count][2] = chessArr1[i][j];
            }
        }
    }
 
    //输出稀疏数组的形式
    System.out.println();
    System.out.println("得到的稀疏数组为：");
    printArray(sparesArr);
    System.out.println();
 
    //下面将稀疏数组恢复成二维数组
    //先读取稀疏数组的第一行元素，根据其数据，创建原始的二维数组
    int chessArr2[][] = new int[sparesArr[0][0]][sparesArr[0][1]];
 
 
    //读取稀疏数组后几行的元素（从第二行开始），并赋值给原始的二维数组即可
 
    for (int i = 1; i < sparesArr.length; i++) {
        chessArr2[sparesArr[i][0]][sparesArr[i][1]] = sparesArr[i][2];
    }
 
    //输出恢复后的二维数组
    System.out.println();
    System.out.println("恢复后的二维数组");
    printArray(chessArr2);
}
 
//打印数组
public static void printArray(int[][] array) {
    for (int i = 0; i < array.length; i++) {
        for (int j = 0; j < array[0].length; j++) {
            System.out.printf("%d\t", array[i][j]);
        }
        System.out.println();
    }
}

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