public class SparseArray {
     
    public static void main(String[] args) throws IOException {
        
        //二维数组 转 稀疏数组 
        int[][] map = new int[11][11];
        int sum = 1;//用来得到稀疏数组有效的行数
        map[1][2] = 2;
        map[2][3] = 3;
        System.out.println("原始数组为：");
        for (int[] m : map) {
            for (int v : m) {
                if(v != 0){
                    sum++;
                }
                System.out.print(v+" ");
            }
            System.out.println();
        }
//        System.out.println("sum="+sum);
        //创建稀疏数组
        int[][] sparseArray = new int[sum][3];
        sparseArray[0][0] = 11;
        sparseArray[0][1] = 11;
        sparseArray[0][2] = sum;
        int cnt = 0;
        for (int i = 0; i < map.length; i++) {
            for (int j = 0; j < map[i].length; j++) {
                if(map[i][j] != 0){
                    ++cnt;
                    sparseArray[cnt][0] = i;
                    sparseArray[cnt][1] = j;
                    sparseArray[cnt][2] = map[i][j];
                }
            }
        }
        
        
        //将稀疏数组保留到磁盘中
        FileWriter fw = new FileWriter(new File("d:/map.txt"));
        for (int i = 0; i < sparseArray.length; i++) {
            for (int j = 0; j < sparseArray[i].length; j++) {
                fw.write(sparseArray[i][j]+"\t");
            }
            fw.write("\r\n");
        }
        fw.close();
        int row = 0;//创建稀疏数组的大小
        String line = "";//一行数据
        BufferedReader br = new BufferedReader(new FileReader(new File("d:/map.txt")));
        while((line = br.readLine())!= null){
            row++;
        }
        int sparseArray2[][] = new int[row][3];
        br.close();
        row = 0;//此时row用来记录行数
        //已经读完文件，所以要重新打开文件，文件指针回到首位
        br = new BufferedReader(new FileReader(new File("d:/map.txt")));
        while((line = br.readLine())!=null){
            String[] temp = line.split("\t");//每一行的数据由\t分隔开
            for(int j = 0; j < temp.length; j++){
                sparseArray2[row][j] = Integer.parseInt(temp[j]);
            }
            row++;
        }
        br.close();
        
        
        System.out.println("稀疏数组为：");
        for (int i = 0; i < sparseArray.length; i++) {
            for (int j = 0; j < sparseArray[i].length; j++) {
                System.out.print(sparseArray[i][j]+" ");
            }
            System.out.println();
        }
        System.out.println("稀疏数组2为：");
        for (int i = 0; i < sparseArray2.length; i++) {
            for (int j = 0; j < sparseArray2[i].length; j++) {
                System.out.print(sparseArray2[i][j]+" ");
            }
            System.out.println();
        }
        
        
        //稀疏数组 转 二维数组
        int[][] map2 = new int[sparseArray[0][0]][sparseArray[0][1]];
        
        for (int i = 1; i < sparseArray.length; i++) {
            map2[sparseArray[i][0]][sparseArray[i][1]] = sparseArray[i][2];
        }
        System.out.println("恢复后的二维数组：");
        for (int[] m2: map2) {
            for (int v2 : m2) {
                System.out.print(v2+" ");
            }
            System.out.println();
        }
    }
}