Méthode numérique Méthode complète d'élimination de l'élément principal pour résoudre des équations linéaires

La question d'origine est triée comme ceci.

Le programme est trié comme ça, trop paresseux pour le changer, presque ça marche, hehe

import java.util.Scanner;

public class Gauss {
    static final int MAXN = 20;
    static double a[][] = new double[MAXN][MAXN];
    static double b[][] = new double[2][MAXN];//我想多了,这里用一维数组就好
    static int num;
    static int x_max;
    static int y_max;

    public static void main(String[] args) {
        System.out.println("输入未知数个数:");
        Scanner sc = new Scanner(System.in);
        num = sc.nextInt();
        System.out.println("输入用矩阵表示的线性方程组:");
        for (int i = 0; i < num; i++) {//输入方程组
            for (int j = 0; j <= num; j++) {
                a[i][j] = sc.nextDouble();
            }
        }

        for (int i = 0; i < num; i++) {//初始化计数数列
            b[0][i] = i;
            b[1][i] = 0;
        }
        for (int j = 0; j < num; j++) {
            a[num][j] = j;
        }
        for (int j = 0; j < num - 1; j++) {
            findMax(j);
        
           sort1(j);

            findMax(j);
       
            sort2(j);

            dengjia(j);


        }

        for (int i = num - 1; i >= 0; i--) {
            jiefangcheng(i);
        }
        for (int j = 0; j < num; j++) {
            System.out.println("x" + (a[num][j] + 1) + "=" + b[1][j]);
        }
    }

    static void sort1(int jj) {//行排序
        for (int j = jj; j < num - 1; j++) {

            for (int k = jj; k < num - 1; k++) {

                if (Math.abs(a[k][x_max]) < Math.abs(a[k + 1][x_max])) {
                    for (int i = jj; i <= num; i++) {
                        double temp = a[k][i];
                        a[k][i] = a[k + 1][i];
                        a[k + 1][i] = temp;
                    }
                }


            }
        }
    }

    static void sort2(int jj) {//列排序
        for (int j = jj; j < num - 1; j++) {

            for (int k = jj; k < num - 1; k++) {

                if (Math.abs(a[y_max][k]) < Math.abs(a[y_max][k+1])) {
                    for (int i = 0; i <= num; i++) {
                        double temp = a[i][k];
                        a[i][k] = a[i][k + 1];
                        a[i][k + 1] = temp;
                    }
                }


            }
        }
    }

    static void findMax(int jj) {
        double max = 0;
        for (int i = jj; i < num; i++) {
            for (int j = jj; j < num; j++) {
                if (Math.abs(a[i][j]) > Math.abs(max)) {
                    max = a[i][j];
                    y_max = i;
                    x_max = j;
                }
            }
        }
    }

    static void dengjia(int jj) {//把原矩阵转化成三角形的
        for (int i = jj + 1; i < num; i++) {
            double k = a[i][jj] / a[jj][jj];
            for (int j = jj; j <= num; j++) {
                a[i][j] = a[i][j] - a[jj][j] * k;
            }
        }

    }

    static void jiefangcheng(int ii) {//解方程
        for (int j = ii + 1; j < num; j++) {
            a[ii][num] -= a[ii][j] * b[1][j];
        }
        b[1][ii] = a[ii][num] / a[ii][ii];

    }

}