Java 稀疏数组

• 当一个数组中大部分元素为0，或者为同一值的数组时，可以使用稀疏数组来保存该数组。

示例：

package com.shun.array;

public class ArrayDemo08 {
    public static void main(String[] args) {
        //稀疏数组
        //创建一个二维数组 11*11的棋盘格    0：代表没有棋子    1：黑棋    2：白棋
        int[][] array1 = new int[11][11];
        array1[1][2] = 1;
        array1[2][3] = 2;

        System.out.println("输出原始的数组");

        for (int[] ints : array1) {
            for (int anInt : ints) {
                System.out.print(anInt+"\t");
            }
            System.out.println();
        }//输出的结果为：
        //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	0

        System.out.println("---------------------------");
        //转化为稀疏数组保存
        //1.先获取有效值的个数
        int sum = 0;
        for (int i = 0; i < 11; i++) {
            for (int j = 0; j < 11; j++) {
                if (array1[i][j]!=0){
                    sum++;
                }
            }
        }
        System.out.println("有效值的个数:"+sum);

        //2.创建一个稀疏数组,并把第一行的值存放进去
        int[][] array2 =new int[sum+1][3];

        array2[0][0] = 11;
        array2[0][1] = 11;
        array2[0][2] = sum;

        //3.把非零的值，存放到稀疏数组中去
        int count = 0;
        for (int i = 0; i < array1.length; i++) {
            for (int j = 0; j < array1[i].length; j++) {
                if (array1[i][j] != 0){
                    count++;
                    array2[count][0] = i;
                    array2[count][1] = j;
                    array2[count][2] = array1[i][j];
                }
            }
        }

        System.out.println("---------------");
        //4.输出稀疏数组
        System.out.println("稀疏数组");
        for (int[] ints : array2) {
            for (int anInt : ints) {
                System.out.print(anInt+"\t");
            }
            System.out.println();
        }//输出的结果为：
        //11    11  	2
        //1 	2	    1
        //2	    3	    2

        //还原稀疏数组
        //1.创建数组
        int[][] array3 =new int[array2[0][0]][array2[0][1]];

        //从稀疏数组中获取非零的元素，并还原值
        for (int i = 1; i < array2.length; i++) {
            array3[array2[i][0]][array2[i][1]] = array2[i][2];
        }

        //打印值
        System.out.println("------------------");
        System.out.println("输出还原数组：");
        for (int[] ints : array3) {
            for (int anInt : ints) {
                System.out.print(anInt +"\t");
            }
            System.out.println();
        }//输出的结果为：
        //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	0

    }
}