package gaodai;import java.util.List;/*** N阶行列式计算* @author 邱万迟**/
public class DeterminantCalculation {public DeterminantCalculation(List<List<Double>> determinant){this.determinant = determinant;this.sign = 1;}private List<List<Double>> determinant;private int sign;private int caculateTimes;/*** 转置*/public void transpose(){int lineNum = determinant.size();int columnNum = determinant.get(0).size();for(int i = 0; i < lineNum; i++){for(int j = i; j < columnNum; j++){double t = determinant.get(i).get(j);determinant.get(i).set(j,determinant.get(j).get(i));determinant.get(j).set(i,t);}}}/*** 获取行列式的值* @return*/public double getValue(){double temp = 1.0;for(int i = 0; i < determinant.size(); i++){temp *= determinant.get(i).get(i);}return Math.round((temp * getSign()) * 100)/100.0;}/*** a行与b行互换(两行互换)* @param determinant 行列式* @param a 行号* @param b 行号* @throws Exception */public void changeLine(int a,int b) throws Exception{if(a < 1 || a > determinant.size() || b < 1 || b > determinant.size()){throw new Exception("输入的行号不合法");}List<Double> aLine = determinant.get(a - 1);List<Double> bLine = determinant.get(b - 1);determinant.set(a - 1, bLine);determinant.set(b - 1, aLine);changeSign();System.out.println("第" + a + "行与" + b + "行互换");}/*** 两列互换* @param a* @param b* @throws Exception */public void changeColumn(int a,int b) throws Exception{if(a < 1 || a > determinant.get(0).size() || b < 1 || b > determinant.get(0).size()){throw new Exception("输入的列号不合法");}for(int i = 0; i < determinant.size(); i++){double temp = determinant.get(i).get(a - 1);determinant.get(i).set(a - 1,determinant.get(i).get(b - 1));determinant.get(i).set(b - 1,formateDouble(temp));}changeSign();}/*** a行加到b行上* @param a* @param b* @throws Exception */public void lineAdd2OtherLine(int a, int b) throws Exception{lineMultiplyNumAdd2OtherLine(1, a, b);}/*** 第a行乘以number 加到第b行上* @param number 乘以的数* @param a行号* @param b行号* @throws Exception */public void lineMultiplyNumAdd2OtherLine(double number,int a, int b) throws Exception{if(a < 1 || a > determinant.size() || b < 1 || b > determinant.size()){throw new Exception("输入的行号不合法");}List<Double> aLine = determinant.get(a - 1);List<Double> bLine = determinant.get(b - 1);for(int i = 0; i < bLine.size(); i++){double temp = bLine.get(i) + aLine.get(i) * number;bLine.set(i, formateDouble(temp));}System.out.println("第" + a + "行乘以" + number + "加到第" + b + "行:");print();}public double formateDouble(double data){return Math.round(data * 10000000000L)/10000000000.0;}/*** a列加到b列* @param a* @param b*/public void columnAdd2OtherColumn(int a, int b){columnMultiplyNumAdd2OtherColumn(1, a, b);}/*** 第a列乘以number 加到第b列上* @param number 乘以的数* @param a行号* @param b行号*/public void columnMultiplyNumAdd2OtherColumn(double number,int a, int b){for(int i = 0; i < determinant.size(); i++){double temp = determinant.get(i).get(b - 1) + determinant.get(i).get(a - 1) * number;determinant.get(i).set(b - 1, temp);}}/*** 校验是否是上三角，不是就的继续计算* @return*/public boolean isCaculate(){boolean hasCaculate = false;for(int i = 0; i < determinant.size(); i++){for(int j = 0; j < i; j++){if(determinant.get(i).get(j) != 0.0){System.out.println("(" + (i + 1) + "," + (j + 1) + ")元素值不为零");hasCaculate = true;break;}}if(hasCaculate){break;}}//System.out.println("isUpperTriangle?>>>>>>>>>>>" + hasCaculate);return hasCaculate;}/*** @throws Exception * 变为上三角* @throws  */public void chang2UpperTriangle() throws Exception{if(!isCaculate()){return;}caculateTimes++;System.out.println("----------------------------------第" + caculateTimes + "次计算----------------------------------");for(int i = 0; i < determinant.size(); i++){for(int j = i + 1; j < determinant.size(); j++){if(determinant.get(i).get(i) == 0){//每一行在对角线上元素是零就互换行changeLine(i + 1, j + 1);print();continue;}double multiplyNum = -1 * determinant.get(j).get(i) / determinant.get(i).get(i);if(multiplyNum == 0){continue;}this.lineMultiplyNumAdd2OtherLine(multiplyNum, (i + 1), (j + 1));}}print();chang2UpperTriangle();}/*** 获取a行b列元素所在的下一个非零元素所在的行* @param a* @param b*/public int getNotZeroLineByColumn(int a,int b){for(int i = a + 1; i < determinant.size(); i++){if(determinant.get(i).get(b) != 0){return i;}}return 0;}/*** 改变符号*/private void changeSign(){this.sign = this.sign * -1;}public void print(){int i = 0,j = 0;for(List<Double> line : determinant){for(double element : line){System.out.print(element);//System.out.print(Math.round(element*100)/100.0);System.out.print("(" + i + "," + j + ")  ");System.out.print("  ");j++;}System.out.println();i++;j = 0;}System.out.println();}public List<List<Double>> getDeterminant() {return determinant;}public void setDeterminant(List<List<Double>> determinant) {this.determinant = determinant;}public int getSign() {return sign;}
}

package gaodai;import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;import org.apache.commons.lang.StringUtils;public class Test {public static void main(String[] args) {int lineNum = 0;Scanner scanner = new Scanner(System.in);boolean flag = true;System.out.println("请输入行列式的阶数,系统会随机生成行列式里的数：");while(flag){ String num = scanner.next();if(StringUtils.isNotBlank(num)){try {lineNum = Integer.valueOf(num);} catch (Exception e) {lineNum = 0;}if(lineNum < 1){System.out.println("请重新输入(需是整数且大于零)");}else{flag = false;}}else{System.out.println("请重新输入(需是整数且大于零)");}}int columnNum = lineNum;List<List<Double>> result = new ArrayList<List<Double>>();for(int i = 0; i < lineNum; i++){List<Double> temp = new ArrayList<Double>();for(int j = 0; j < columnNum; j++){temp.add((double) (int)(Math.random()*10 + 1));}result.add(temp);}DeterminantCalculation determinant = new DeterminantCalculation(result);System.out.println("初始化行列式:");determinant.print();determinant.transpose();determinant.print();try {determinant.chang2UpperTriangle();} catch (Exception e) {e.printStackTrace();}determinant.print();System.out.println("行列式值为:" + determinant.getValue());}}

JAVA实现的N阶行列式计算，一起分享学习，有不足之处还望指正批评。