UPD20190318
我发现写错了…交换行的时候没写变号…
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上课闲着没事…用Java写了个求行列式的
还是高斯消元那样求
我的命名还是一如既往的风骚233
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import java.util.Scanner;
class QAQ {
private double eps = 1e-6;
private int n;
private double[][] a = new double[55][55];
private boolean cmp(double a, double b) {
return Math.abs(a-b)<eps;
}
public void init() {
Scanner sn = new Scanner(System.in);
n = sn.nextInt();
for(int i=1; i<=n; i++) {
for(int j=1; j<=n; j++) {
a[i][j] = sn.nextDouble();
}
}
}
public double Solve() {
double ans = 1;
for(int i=1; i<=n; i++) {
if(cmp(a[i][i],0)) {
ans = -ans;
int flag = 0;
for(int j=i+1; j<=n; j++) if(!cmp(a[j][i],0)) flag = j;
if(flag==0) return 0;
for(int j=i; j<=n; j++) {
double t=a[i][j];
a[i][j]=a[flag][j];
a[flag][j]=t;
}
}
for(int j=i+1; j<=n; j++) {
double t=a[j][i]/a[i][i];
for(int k=i; k<=n; k++)
a[j][k]-=t*a[i][k];
}
}
for(int i=1; i<=n; i++) ans*=a[i][i];
return ans;
}
public void print() {
for(int i=1; i<=n; i++) {
for(int j=1; j<=n; j++) {
System.out.print(a[i][j] + " ");
}System.out.println("");
}
}
public static void main(String[] args) {
QAQ qwq = new QAQ();
qwq.init();
System.out.println("ans = " + qwq.Solve());
qwq.print();
}
}
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