WA on #3 #9

貌似是判不出无解和无数解，求调

#include <iostream>
#include <cmath>

using namespace std;

int n;
double a[59][59], b[59];

void gaussianElimination() {
	for (int i = 1; i <= n; i++) {
		int p = i;
		for (int j = i + 1; j <= n; j++) {
			if (fabs(a[j][i]) >= fabs(a[p][i])) {
				p = j;
			}
		}
		swap(a[i], a[p]);
		swap(b[i], b[p]);
		if (fabs(a[i][i]) < 1e-12) {
			if (fabs(b[i]) < 1e-12) {
				cout << "-1";
			} else {
				cout << "0";
			}
			exit(0);
		}
		double co = a[i][i];
		for (int j = i; j <= n; j++) {
			a[i][j] /= co;
		}
		b[i] /= co;
		for (int j = i + 1; j <= n; j++) {
			double fac = a[j][i];
			for (int k = i; k <= n; k++) {
				a[j][k] -= fac * a[i][k];
			}
			b[j] -= fac * b[i];
		}
	}
	for (int i = n; i >= 1; i--) {
	    for (int j = i - 1; j >= 1; j--) {
	        double fac = a[j][i];
	        for (int k = i; k <= n; k++) {
	            a[j][k] -= fac * a[i][k];
	        }
	        b[j] -= fac * b[i];
	    }
	}
}

int main() {
//	freopen("9.in", "rt", stdin);
//	freopen("9.out", "wt", stdout);
    cin >> n;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            cin >> a[i][j];
        }
        cin >> b[i];
    }
    gaussianElimination();
    for (int i = 1; i <= n; i++) {
		cout << "x" << i << "=";
		printf("%.2lf\n", b[i]); 
	}
}