稀疏数组

用途：将普通数组转为稀疏数组来达到节省空间的目的

介绍：

代码：

import cn.hutool.core.util.ObjectUtil;
import org.junit.Test;

public class SparseArrayTest {
    @Test
    public void test() {
        Integer[][] integers = new Integer[6][7];
        integers[0][3] = 22;
        integers[0][6] = 15;
        integers[1][1] = 11;
        integers[1][5] = 17;
        integers[2][3] = -6;
        integers[3][5] = 39;
        integers[4][0] = 91;
        integers[5][2] = 28;
        System.out.println("~~~原始数组~~~");
        SparseArray.showArray(integers);
        Integer[][] sparseArray = SparseArray.toSparseArray(integers);
        System.out.println("~~~稀疏数组~~~");
        SparseArray.showArray(sparseArray);
        Integer[][] ordinaryArray = SparseArray.toOrdinaryArray(sparseArray);
        System.out.println("~~~普通数组~~~");
        SparseArray.showArray(ordinaryArray);
    }
}

class SparseArray {

    /**
     * 普通数组转为稀疏数组
     * @param source
     * @return
     */
    public static Integer[][] toSparseArray(Integer[][] source) {
        //对source的有效数据进行计数
        int count = 0;
        for (int i = 0; i < source.length; i++) {
            for (int j = 0; j < source[i].length ; j++) {
                if (ObjectUtil.isNotNull(source[i][j])) {
                    count++;
                }
            }
        }
        //创建稀疏数组
        Integer[][] sparseArray = new Integer[count + 1][3];
        //设置稀疏数组第一行的数据
        sparseArray[0][0] = source.length;
        sparseArray[0][1] = source[0].length;
        sparseArray[0][2] = count;
        //将有效数据放进稀疏数组
        count = 0;
        for (int i = 0; i < source.length; i++) {
            for (int j = 0; j < source[i].length ; j++) {
                if (ObjectUtil.isNotNull(source[i][j])) {
                    count ++;
                    sparseArray[count][0] = i;
                    sparseArray[count][1] = j;
                    sparseArray[count][2] = source[i][j];
                }
            }
        }
        return sparseArray;
    }

    /**
     * 稀疏数组转为普通数组
     * @param source
     * @return
     */
    public static Integer[][] toOrdinaryArray(Integer[][] source) {
        //新建普通数组
        Integer[][] ordinaryArray = new Integer[source[0][0]][source[0][1]];
        for (int i = 1; i < source.length; i++) {
            ordinaryArray[source[i][0]][source[i][1]] = source[i][2];
        }
        return ordinaryArray;
    }

    /**
     * 在控制台打印数组
     * @param source
     */
    public static void showArray(Integer[][] source) {
        for (int i = 0; i < source.length; i++) {
            for (int j = 0; j < source[i].length; j++) {
                if (ObjectUtil.isNull(source[i][j])) {
                    System.out.printf("00\t");
                    continue;
                }
                System.out.printf("%d\t", source[i][j]);
            }
            System.out.println();
        }
    }
}