稀疏数组

以下代码把11*11的棋盘转化为稀疏数组，再把稀疏数组转化为普通的矩阵（即棋盘）。

package com.cxf.array;

import java.util.Arrays;

public class Demo2 {
    public static void main(String[] args) {
        int[][] chess1 = new int[11][11];
        int num_val = 0;
        int count = 1;
        chess1[2][3] = 1;
        chess1[3][4] = 2;

        System.out.println("Original chess board:");
        for (int i = 0; i < 11; i++) {
            for (int j = 0; j < 11; j++) {
                System.out.print(chess1[i][j]+"\t");
                if(chess1[i][j] != 0) {
                    num_val++;
                }
            }
            System.out.println();
        }

        int[][] sparse = new int[num_val + 1][3];   //create a sparse matrix
        sparse[0][0] = 11;
        sparse[0][1] = 11;
        sparse[0][2] =num_val;
        for (int i = 0; i < 11; i++) {
            for (int j = 0; j < 11; j++) {
                if(chess1[i][j] != 0) {
                    sparse[count][0] = i;
                    sparse[count][1] = j;
                    sparse[count][2] = chess1[i][j];
                    count++;
                }
            }
        }
        System.out.println("==========================================");
        System.out.println("sparce matrix:");
        for (int i = 0; i < num_val + 1; i++) {
            System.out.println(Arrays.toString(sparse[i]));
        }
        System.out.println("==========================================");

        System.out.println("turn the sparce matrix to chess board:");
        int[][] chess2 = new int[sparse[0][0]][sparse[0][1]];
        for (int i = 1; i <= sparse[0][2]; i++) {
            chess2[sparse[i][0]][sparse[i][1]] = sparse[i][2];
        }

        //print chess2
        for (int[] ints : chess2) {
            for (int anInt : ints) {
                System.out.print(anInt + "\t");
            }
            System.out.println();
        }
    }
}

输出结果：

Original chess board:
0	0	0	0	0	0	0	0	0	0	0	
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	
==========================================
sparce matrix:
[11, 11, 2]
[2, 3, 1]
[3, 4, 2]
==========================================
turn the sparce matrix to chess board:
0	0	0	0	0	0	0	0	0	0	0	
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	

稀疏数组只记录普通数组中特殊点的位置和值。