Sparse array (nonlinear structure)

When in an array Most elements are ０, Or for Array of the same value when , You can use a sparse array to hold the array .

The transformation process

Gobang board > Two dimensional array > Sparse array > Storage

The illustration

• 11*11 Two dimensional array of , among 1 The location of the for [1] [2],2 The location of the for [2] [3]
• 3*3 Sparse two-dimensional array of , The first row of data is Row column value and Number of non-zero values , The data in the last few lines is Stored non-zero value

Code

Pay attention to the ideas of the notes ~

package com.atguigu.sparsearray;

//author qij
public class SparseArray {
    

	public static void main(String[] args) {
    
		//  Create an original two-dimensional array  11 * 11
		int chessArr1[][] = new int[11][11];
		chessArr1[1][2] = 1;
		chessArr1[2][3] = 2;
		chessArr1[4][5] = 2;
		//  Output the original two-dimensional array 
		System.out.println(" The original two-dimensional array ~~");
		for (int[] row : chessArr1) {
    
			for (int data : row) {
    
				System.out.printf("%d\t", data);
			}
			System.out.println();
		}

		//  Put two-dimensional array   turn   Sparse array 
		// 1.  First, traverse the two-dimensional array   Get the blame 0 Number of data 
		int sum = 0;
		for (int i = 0; i < 11; i++) {
    
			for (int j = 0; j < 11; j++) {
    
				if (chessArr1[i][j] != 0) {
    
					sum++;
				}
			}
		}

		//2. Create the corresponding sparse array 
		int sparseArr[][] = new int[sum + 1][3];
		//3. Assign a value to the first row of the sparse array 
		sparseArr[0][0] = 11;
		sparseArr[0][1] = 11;
		sparseArr[0][2] = sum;
		
		//4. Traversing a two-dimensional array , Will not 0 The value of is stored in  sparseArr in 
		int count = 0; //count  It's the number one non 0 data 
		for (int i = 0; i < 11; i++) {
    
			for (int j = 0; j < 11; j++) {
    
				if (chessArr1[i][j] != 0) {
    
					count++;
					sparseArr[count][0] = i;
					sparseArr[count][1] = j;
					sparseArr[count][2] = chessArr1[i][j];
				}
			}
		}
		
		// Output 
		System.out.println();
		System.out.println(" Get the sparse array as ~~~~");
		for (int i = 0; i < sparseArr.length; i++) {
    
			System.out.printf("%d\t%d\t%d\t\n", sparseArr[i][0], sparseArr[i][1], sparseArr[i][2]);
		}
		System.out.println();
		
		// Sparse array   recovery   The original two-dimensional array 
		//1.  First read the first row of the sparse array , According to the data in the first line , Create the original two-dimensional array 
		int chessArr2[][] = new int[sparseArr[0][0]][sparseArr[0][1]];
		
		//2.  After reading the sparse array a few lines of data （ Start with the second line ）, And give it to   The original two-dimensional array   that will do 
		for(int i = 1; i < sparseArr.length; i++) {
    
			chessArr2[sparseArr[i][0]][sparseArr[i][1]] = sparseArr[i][2];
		}
		
		//  Output 
		System.out.println();
		System.out.println(" Recovered 2D array ");
		for (int[] row : chessArr2) {
    
			for (int data : row) {
    
				System.out.printf("%d\t", data);
			}
			System.out.println();
		}
	}

}

Output results ：