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This article mainly introduces java how to achieve the original array and sparse array conversion related knowledge, the content is detailed and easy to understand, simple and fast operation, has a certain reference value, I believe that after reading this java how to achieve the original array and sparse array conversion article will have a harvest, let's take a look at it.

1. What is it?

For example, there is an 11-11 Gobang board, we want to use a program simulation, it must be a two-dimensional array. Then use 1 for sunspot and 2 for white spot. If there is only one black spot and one white spot on the chessboard, then there is only one 1 and one 2 in this two-dimensional array, and the others are meaningless and do not represent the zeros of any chess pieces, as follows:

0 0 0

0 0 0 1 0 0 0

0 0 0 2 0 0 0

0 0 0

……

When most of the elements in an array are zero, or the same value, you can save the array with a sparse array. Why would you do that? Because it can save space.

2. How to use it?

The original array has several rows and columns, and how many different values record the rows and values of elements with different values in a small array, which is called a sparse array

3. Case:

The following raw array of 6 * 7 is available:

0 0 0 22 0 0 15

0 11 0 0 0 17 0

0 000-6 000 0

0 0 0 39 0

91 0 0 0

0 0 28 0 0 0

First of all, the first row of the sparse array is the first row of the record element array, the first row and the second column is the number of columns of the original array, and the first row and the third column is that the original array has several different values (except 0). So the sparse array line should be:

Row and column value

6 7 8

The second row of the sparse array begins, and each row records the row, column, and size of the non-zero value in the original array. For example, if the second row records the rows, columns, and values of 22 in the original array, then the second row of the sparse array is:

Row and column value

0 3 22

Then use this method to record the relevant information of 15, 11, 17,-6, 39, 91, 28, so the sparse array transformed from the original array is:

Row and column value

6 7 8

0 3 22

0 6 15

11 11

1 5 17

2 3-6

3 5 39

4 0 91

5 2 28

This turns a 6 * 7 array into a 9 * 3 array, achieving the effect of compression.

4. The idea of converting original array to sparse array:

The original array changes to sparse array:

Traversing the two-dimensional array to get the number of valid arrays count; can create a sparse array int [count + 1] [3] according to count; store the valid array into the sparse array

Sparse array to original array:

Read the first row of the sparse array, according to the first row array, you can know how many rows and columns there are in the original array, and then create the original array; read the array in the next few rows of the sparse array and assign values to the original array

5. Code practice:

Public class SparseArray {

Public static void main (String [] args) {

/ / create a raw array of 11 * 11

Int [] arr1 = new int [11] [11]

Arr1 [1] [2] = 1

Arr1 [2] [3] = 2

/ / convert original array to sparse array

/ / 1. Traverse to get the number and rows of non-zero data

Int count = 0

Map map = new HashMap ()

For (int I = 0; I < arr1.length; iTunes +) {

For (int j = 0; j < arr1 [I] .length; jacks +) {

If (arr1 [I] [j]! = 0) {

Count + +

Map.put (I + "," + j, arr1 [I] [j])

}

}

}

/ / 2. Create a sparse array

Int [] [] sparseArr = new int [count + 1] [3]

SparseArr [0] [0] = arr1.length

SparseArr [0] [1] = arr1 [0] .length

SparseArr [0] [2] = count

/ / 3. Assign values to sparse arrays

Int row = 1

For (String key: map.keySet ()) {

String [] ij = key.split (",")

Int I = Integer.parseInt (ij [0])

Int j = Integer.parseInt (ij [1])

SparseArr [row] [0] = I

SparseArr [row] [1] = j

SparseArr [row] [2] = map.get (key)

Row + +

}

/ / 4. Traversing sparse array

For (int I = 0; I < sparseArr.length; iTunes +) {

For (int j = 0; j < sparseArr [I]. Length; jacks +) {

System.out.print (sparseArr [I] [j] + "")

}

System.out.println ("\ r\ n")

}

/ / sparse array restores the original array

/ / 1. Create the original array based on the first row, the first column and the second column

Int I = sparseArr [0] [0]

Int j = sparseArr [0] [1]

Int [] [] arr2 = new int [I] [j]

/ / 2. Assign a value to the original array

For (int k = 1; k < sparseArr.length; knot +) {

Int x = sparseArr [k] [0]

Int y = sparseArr [k] [1]

Int val = sparseArr [k] [2]

Arr2 [x] [y] = val

}

/ / 3. Traversing transformed array

For (int a = 0; a < arr2.length; aura +) {

For (int b = 0; b < arr2 [a] .length; baked +) {

System.out.print (ARR2 [a] [b] + "")

}

System.out.println ("\ r\ n")

}

}

}

The above code realizes the conversion between the original array and the sparse array, and the flexible use of sparse array can save running memory and improve program performance.

This is the end of the article on "how java converts raw arrays to sparse arrays". Thank you for reading! I believe you all have a certain understanding of the knowledge of "how to convert original arrays to sparse arrays by java". If you want to learn more, you are welcome to follow the industry information channel.

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