稀疏数组

public class sparseArray {
    public static void main(String[] args) {
        int[][] array = new int[11][11];
        array[1][3] = 1;
        array[2][4] = 2;
        for (int[] i:array) {
            for (int i1:i){
                System.out.print(i1+"\t");
            }
            System.out.println();
        }
        //稀疏数组
        System.out.println("=================================");
        //计算非零数的个数
        int sum = 0;
        for (int i = 0; i < array.length; i++) {
            for (int j = 0; j < array[i].length; j++) {
                if (array[i][j] != 0){
                    sum++;
                }
            }
        }
        int[][] array1 = new int[sum+1][3];
        array1[0][0] = 11;
        array1[0][1] = 11;
        array1[0][2] = sum;
        //非零赋值
        int count = 1;
        for (int i = 0; i < array.length; i++) {
            for (int j = 0; j < array[i].length; j++) {
                if (array[i][j] != 0){
                    array1[count][0] = i;   //把行的位置赋值
                    array1[count][1] = j;   //把列的位置赋值
                    array1[count][2] = array[i][j];     //数值赋值
                    count++;
                }
            }
        }
        //打印输出
        System.out.println("稀疏数组");
        for (int i = 0; i < array1.length; i++) {
            System.out.println(array1[i][0]+"\t"+
                    array1[i][1]+"\t"+array1[i][2]);

        }
        //稀疏数组还原
        int[][] array2 = new int[array1[0][0]][array1[0][1]];
        for (int i = 1; i < array1.length; i++) {   //i要从1开始，不能从0，会下标越界，因为索引是从0到10，读取11会越界
            array2[array1[i][0]][array1[i][1]] = array1[i][2];
            }
        for (int[] i:array2) {
            for (int i1:i){
                System.out.print(i1+"\t");
            }
            System.out.println();
        }
    }
}

输出结果：

0    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    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    0    0    0    0    0    0    0    0    0    
=================================
稀疏数组
11    11    2
1    3    1
2    4    2
0    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    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    0    0    0    0    0    0    0    0    0    

稀疏数组例子如图：