稀疏数组介绍

• 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。

• 稀疏数组的处理方式是：

  • 记录数组一共有几行几列，有多少个不同值
  • 把具有不同值的元素和行列及值记录在一个小规模的数组中，从而缩小程序的规模

• 如下图:左边是原始数组，右边是稀疏数组

  • 

package com.guan.array;

import java.util.Arrays;

public class ArrayDemo08 {


    public static void main(String[] args) {
        int[][] array1 = new int[11][11];
        array1[1][2] = 1;
        array1[2][3] = 1;
        //输出原始数组
        System.out.println("输出原始数组");
        for (int[] ints : array1) {//arrays.for外层输出  打印二维数组
            for (int anInt : ints) {//ints.for内层循环
                System.out.print(anInt+"\t");
            }
            System.out.println();
        }
        System.out.println("===============");
        //转化为稀疏数组
        //1。获取有效值的个数
        int sum = 0;
        for (int i = 0; i <array1.length ; i++) {
            for (int j = 0; j <array1[i].length ; j++) {
                if (array1[i][j]!= 0){
                    sum++;
                }
            }
        }
        System.out.println("sun = "+sum);
        System.out.println("===============");

        //2。创建稀疏数组
        int[][] arrary2 = new int[sum+1][3];

        arrary2[0][0] = 11;
        arrary2[0][1]= 11;
        arrary2[0][2]= sum;
        //遍历二维数组，将非零的值，存放在稀疏数组中
        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++;
                    arrary2[count][0]= i;
                    arrary2[count][1]= j;
                    arrary2[count][2]= array1[i][j];

                }
            }
        }
        for (int i = 0; i < arrary2.length; i++) {
//            System.out.println(arrary2[i][0]+"\t"
//            +arrary2[i][1]+"\t"
//            +arrary2[i][2]+"\t");
            for (int j = 0; j < arrary2[i].length; j++) {
                System.out.print(arrary2[i][j]+"\t");
            }
            System.out.println();
        }

        //还原稀疏数组
        System.out.println("============");
        System.out.println("还原");

        //1.读取稀疏数组
        int[][] array3 = new int[arrary2[0][0]][arrary2[0][1]];
        //.给其中元素还原值
        for (int i = 1; i < arrary2.length; i++) {
            array3[arrary2[i][0]][arrary2[i][1]] = arrary2[i][2];
        }

        //3.打印数组
        for (int[] ints : array3) {
            for (int anInt : ints) {
                System.out.print(anInt+"\t");
            }
            System.out.println();
        }
        }
}

输出原始数组
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	1	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
===============
sun = 2
===============
11	11	2	
1	2	1	
2	3	1	
============
还原
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	1	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0	
0	0	0	0	0	0	0	0	0	0	0