1 import java.io.*;
  2 
  3 /**
  4  * @author ZhiYi Li
  5  * @create 2020/8/24 10:47
  6  * 普通矩陣轉稀疏矩陣，稀疏矩陣轉普通矩陣，稀疏矩陣的物理儲存
  7  */
  8 public class SparseArr {
  9     public static void main(String[] args) {
 10         //構建一個普通矩陣
 11         int[][] first = new int[11][12];
 12         first[2][2]=1;
 13
 
         first[3][4]=2;
 14         //輸出普通矩陣
 15         System.out.println("生成的普通稀疏矩陣：");
 16         for (int i = 0; i < 11; i++) {
 17             for (int j = 0; j < 10; j++) {
 18                 System.out.print(first[i][j]+" ");
 19             }
 20             System.out.println();
 21         }
 
 22         //轉換為稀疏矩陣
 23         //遍歷普通矩陣查詢非0元素
 24         int sum=0;
 25         for (int i = 0; i < 11; i++) {
 26             for (int j = 0; j < 10; j++) {
 27                 if(first[i][j]!=0){
 28                     sum++;
 29                 }
 30             }
 31         }
 32         //構建稀疏矩陣
 

 33         int[][] second = new int[sum+1][3];
 34         //存入第一行
 35         second[0][0] = first.length;
 36         second[0][1] = first[0].length;
 37         second[0][2] = sum;
 38         //遍歷有效節點依次存入稀疏矩陣
 39         int temp = 0;
 40         for (int i = 0; i < first.length; i++) {
 41             for (int j = 0; j < first[0].length; j++) {
 42                 if(first[i][j]!=0){
 43                     temp++;
 44                     second[temp][0] = i;
 45                     second[temp][1] = j;
 46                     second[temp][2] = first[i][j];
 47                 }
 48             }
 49         }
 50         //輸出稀疏矩陣
 51         System.out.println("轉換後的稀疏矩陣如下：");
 52         for (int[] ints : second) {
 53             for (int j : ints) {
 54                 System.out.print(j + " ");
 55             }
 56             System.out.println();
 57         }
 58         //稀疏矩陣轉普通矩陣
 59         System.out.println("稀疏矩陣轉普通矩陣：");
 60         int[][] four =new int[second[0][0]][second[0][1]];
 61         for (int i = 1; i < second.length; i++) {
 62             four[second[i][0]][second[i][1]] = second[i][2];
 63         }
 64         for(int[] ints:four){
 65             for (int item : ints){
 66                 System.out.print(item+ " ");
 67             }
 68             System.out.println();
 69         }
 70         //物理儲存稀疏矩陣
 71         try {
 72             FileWriter file = new FileWriter("test.data");
 73             BufferedWriter writer  =new BufferedWriter(file);
 74             for(int[] data : second){
 75                 for(int item : data){
 76                     writer.write(item +" ");
 77                 }
 78                 writer.newLine();//檔案換行
 79             }
 80             writer.close();
 81             file.close();
 82         } catch (IOException e) {
 83             e.printStackTrace();
 84         }
 85 
 86         //讀取並輸出普通矩陣
 87         System.out.println("物理讀取稀疏矩陣如下：");
 88         try {
 89             FileReader fileReader = new FileReader("test.data");
 90             BufferedReader bufferedReader = new BufferedReader(fileReader);
 91             String str = bufferedReader.readLine();
 92             String[] s = str.split(" ");
 93             int[][] third = new int[Integer.parseInt(s[0])][Integer.parseInt(s[1])];
 94             while ((str = bufferedReader.readLine())!=null){
 95                 String[] s1 = str.split(" ");
 96                 third[Integer.parseInt(s1[0])][Integer.parseInt(s1[1])] = Integer.parseInt(s1[2]);
 97             }
 98             for (int[] ints : third) {
 99                 for (int j : ints) {
100                     System.out.print(j + " ");
101                 }
102                 System.out.println();
103             }
104             bufferedReader.close();
105             fileReader.close();
106         } catch (IOException e) {
107             e.printStackTrace();
108         }
109     }
110 }