当一个数组在中大部分元素为0，或者为同一个值的数组时，可以使用稀疏数组来保存该数组。
稀疏数组的处理方法;
- 记录数组一共有几行几列，有多少个不同的值。
- 把具有不同值的元素的行列有值记录在一个小规模的数组中，从而缩小程序的规模。
由7x6的数组转换成3x9的稀疏数组
package jiegou;
import javax.management.relation.Role;
import javax.swing.*;
public class SparseArray {
public static void main(String[] args) {
// 创建一个原始的二维数组 11*11
// 0 表示没有 1 黑子 2 蓝子
int row = 11;
int col = 11;
Sparse sparse = new Sparse();
int[][] chessArr = sparse.createArray(row,col);
System.out.println("原始的数组");
sparse.printArray(chessArr);
int[][] sparseArr = sparse.arrayToSparse(chessArr);
// 输出
System.out.println("稀疏数组数组");
sparse.printArray(sparseArr);
// 转行回原始数组
int[][] oldArr = sparse.sparseToArray(sparseArr);
// 输出
System.out.println("还原后的数组");
sparse.printArray(oldArr);
}
}
class Sparse
{
// 创建一个原始数组
public int[][] createArray(int row,int col)
{
int[][] array = new int[row][col];
array[1][2] = 1;
array[2][3] = 2;
array[3][4] = 2;
return array;
}
// 打印二维数组
public void printArray(int[][] array)
{
for(int[] item : array) {
for(int data : item) {
System.out.printf("%d ",data);
}
System.out.println();
}
}
// 数组转为稀疏数组
public int[][] arrayToSparse(int[][] chessArr)
{
// 遍历原始数组得到有效的非 0 个数
int sum = 0,row = 0,col=0;
row = chessArr.length;
col = chessArr[0].length;
for(int[] item : chessArr) {
for(int data : item) {
if(data != 0 ){
sum++;
}
}
}
System.out.printf("sum=%d
",sum);
// 创建对应的稀疏数组 第三行3是固定的 第一个二个存几行几列 所以行数是个数+1(sum+1)
int[][] sparseArr = new int[sum+1][3];
// 给稀疏数组赋值
sparseArr[0][0] = row; // 总行数
sparseArr[0][1] = col; // 总列数
sparseArr[0][2] = sum; // 总数
//遍历二维数组 将非 0 的值存入到稀疏数组
// 设置一个计数器 从第二行开始
int count = 1;
for(int i=1;i<row;i++){
for(int j=0;j<col;j++){
if(chessArr[i][j] != 0) {
sparseArr[count][0] = i; // 这个非 0 所在的行
sparseArr[count][1] = j; // 这个非 0 所在的列
sparseArr[count][2] = chessArr[i][j]; //值
count++;
}
}
}
return sparseArr;
}
// 稀疏数组转为正常数组 第一行的第一列是行数 第二个是列数 第三个是非 0 的总数
public int[][] sparseToArray(int[][] array)
{
int row ,col;
row = array[0][0];
col = array[0][1];
int[][] arr = new int[row][col];
if(array[0][2] > 0) {
for(int i=1;i< array.length;i++){
for (int j=0;j<3;j++){
arr[array[i][0]][array[i][1]] = array[i][2]; // 第三个是值
}
}
}
return arr;
}
}
/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=65502:/Applications/IntelliJ IDEA.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home/lib/tools.jar:/Users/mac/www/java/shujujiegou/out/production/shujujiegou jiegou.SparseArray
原始的数组
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 2 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
sum=3
稀疏数组数组
11 11 3
1 2 1
2 3 2
3 4 2
还原后的数组
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 2 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
Process finished with exit code 0