02_稀疏数组

01_概念

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 02_使用场景

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03_压缩步骤

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 04_Java实现

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 05_Java实现(稠密数组压缩成稀疏数组、稀疏数组解压成稀疏数组)

package DataStructureReview;

public class SparseArrayDemo {
    public static void main(String[] args) {
        //准备一个9*9的数组
        int[][] arr = new int[4][4];
        arr[0] = new int[]{1, 0, 0, 0, 0, 0, 0};
        arr[1] = new int[]{0, 2, 0, 0, 88, 0, 0};
        arr[2] = new int[]{0, 0, 3, 0, 0, 0, 0};
        arr[3] = new int[]{0, 0, 0, 4, 0, 0, 9};
        int[][] sparse = UtilityClass.dense2sparse(arr);
        UtilityClass.printArray(sparse);
        System.out.println("=========================");
        UtilityClass.printArray(UtilityClass.sparse2dense(sparse));

    }
}

class UtilityClass {
    //将稠密数组压缩成稀疏数组,默认无效数据为0
    public static int[][] dense2sparse(int[][] arr) {
        //1.判断是否为有效压缩
        int rowNum = arr.length;
        int colNum = arr[0].length;
        int num = 0;
        for (int i = 0; i < rowNum; i++) {
            for (int i1 = 0; i1 < colNum; i1++) {
                if (arr[i][i1] != 0) {
                    num++;
                }
            }
        }
        if ((rowNum * colNum / 3 - 1) < num) {
            throw new RuntimeException("压缩无效，无法进行压缩");
        }
        //2.将稠密数组压缩成稀疏数组
        int[][] spaArr = new int[num + 1][3];
        spaArr[0] = new int[]{rowNum, colNum, num};
        int cur = 1;
        for (int i = 0; i < rowNum; i++) {
            for (int i1 = 0; i1 < colNum; i1++) {
                if (arr[i][i1] != 0) {
                    spaArr[cur][0] = i;
                    spaArr[cur][1] = i1;
                    spaArr[cur][2] = arr[i][i1];
                    cur++;
                }
            }
        }
        return spaArr;
    }

    //打印2维数组
    public static void printArray(int[][] arr) {
        int rowNum = arr.length;
        int colNum = arr[0].length;

        for (int i = 0; i < rowNum; i++) {
            for (int i1 = 0; i1 < colNum; i1++) {
                System.out.printf("%d  ", arr[i][i1]);
            }
            System.out.println();
        }
    }

    //将稀疏数组还原成稠密数组
    public static int[][] sparse2dense(int[][] arr) {
        int row_num = arr[0][0];
        int clo_num = arr[0][1];
        int[][] dense_arr = new int[row_num][clo_num];
        int rowNum = arr.length;
        int colNum = arr[0].length;

        for (int i = 1; i < rowNum; i++) {
            int row = arr[i][0];
            int col = arr[i][1];
            int value = arr[i][2];
            dense_arr[row][col] = value;
        }

        return dense_arr;
    }


}