［算法］矩阵的基本运算(Java实现)

package 基本矩阵运算;

public class BasicMatrixMath {

public final static int OPERATION_ADD = 1;
public final static int OPERATION_SUB = 2;
public final static int OPERATION_MUL = 3;

/**
* To be able to add two matrices, they must be of the same size
*
* @param matrixa
* @param matrixb
*/
public int[][] add(int[][] matrixa, int[][] matrixb) {
int[][] result = new int[matrixa.length][matrixb[0].length];
if (legalOperation(matrixa, matrixb, OPERATION_ADD)) {
for (int i = 0; i < matrixa.length; i++) {
for (int j = 0; j < matrixa[0].length; j++) {
result[i][j] = matrixa[i][j] + matrixb[i][j];
}
}
}
return result;
}

/**
* To be able to substract two matrices, they must be of the same size
*
* @param matrixa
* @param matrixb
*/
public int[][] substract(int[][] matrixa, int[][] matrixb) {
int[][] result1 = new int[matrixa.length][matrixb[0].length];
if (legalOperation(matrixa, matrixb, OPERATION_SUB)) {

for (int i = 0; i < matrixa.length; i++) {
for (int j = 0; j < matrixa[0].length; j++) {
result1[i][j] = matrixa[i][j] - matrixb[i][j];
}
}
}
return result1;
}

/**
*
* @param matrixa
* @param matrixb
*/
public int[][] multiplication(int[][] matrixa, int[][] matrixb) {
if (legalOperation(matrixa, matrixb, OPERATION_MUL)) {
int[][] result2 = new int[matrixa.length][matrixb[0].length];
for (int i = 0; i < matrixa.length; i++) {
for (int j = 0; j < matrixa[0].length; j++) {
result2[i][j] = calculateSingleResult(matrixa, matrixb, i, j);
}
}
return result2;
} else {
return null;
}
}

private int calculateSingleResult(int[][] matrixa, int[][] matrixb, Integer row, int col) {
int result = 0;
for (int i = 0; i < matrixa[0].length; i++) {
result += matrixa[row][i] * matrixb[i][col];
}
return result;
}

/**
* @param matrixa
* @param b
*/
public int[][] multiplication(int[][] matrixa, int b) {
int[][] result3 = new int[matrixa.length][matrixa[0].length];
for (int i = 0; i < matrixa.length; i++) {
for (int j = 0; j < matrixa[0].length; j++) {
result3[i][j] = matrixa[i][j] * b;
}
}
return result3;
}

/**
* validate whether the parameters is valid parameters.
*
* @param a
* @param b
* @param type
* @return
*/
private boolean legalOperation(int[][] a, int[][] b, int type) {
boolean legal = true;
if (type == OPERATION_ADD || type == OPERATION_SUB) {
if (a.length != b.length || a[0].length != b[0].length) {
legal = false;
}
} else if (type == OPERATION_MUL) {
if (a[0].length != b.length) {
legal = false;
}
}
return legal;
}

public static void main(String[] args) {
int[][] a = new int[][] { { 1, 2 }, { 3, 4 } };
int[][] b = new int[][] { { 7, 8 }, { 6, 5 } };
BasicMatrixMath bmm = new BasicMatrixMath();
System.out.println("addition two matrix");
int[][] result = bmm.add(a, b);
for (int i = 0; i < result.length; i++) {
for (int j = 0; j < result[0].length; j++) {
System.out.print("\t" + result[i][j]);
}
System.out.println();
}
System.out.println("substract two matrix");
int[][] result1 = bmm.substract(a, b);
for (int i = 0; i < result1.length; i++) {
for (int j = 0; j < result1[0].length; j++) {
System.out.print("\t" + result1[i][j]);
}
System.out.println();
}
System.out.println("multiplex one matrix");
result = bmm.multiplication(a, 3);
for (int i = 0; i < result.length; i++) {
for (int j = 0; j < result[0].length; j++) {
System.out.print("\t" + result[i][j]);
}
System.out.println();
}
System.out.println("multiplex two matrix");
result = bmm.multiplication(a, b);
for (int i = 0; i < result.length; i++) {
for (int j = 0; j < result[0].length; j++) {
System.out.print("\t" + result[i][j]);
}
System.out.println();
}

}

}