gistfile1.cpp

#include <cmath>

const int MAXN = 100;
const double EPS = 1e-10;

//列主元gauss消去求解a[][]x[]=b[]
//返回是否有唯一解,若有解在b[]中
bool gaussCpivot(int n, double a[][MAXN], double b[]) {
	int i, j, k, row;
	double maxp, t;
	for (k = 0; k < n; k++) {
		for (maxp = 0, i = k; i < n; i++) {
			if (fabs(a[i][k]) > fabs(maxp)) {
				maxp = a[row = i][k];
			} 
		}
		if (fabs(maxp) < EPS) {
			return false;
		}
		if (row != k) {
			for (j = k; j < n; j++) {
				swap(a[k][j], a[row][j]);
			}
		swap(b[k], b[row]);
		}
		for (j = k + 1; j < n; j++) {
			a[k][j] /= maxp;
			for (i = k + 1; i < n; i++) {
				a[i][j] -= a[i][k] * a[k][j];
			} 
		}
		b[k] /= maxp;
		for (i = k + 1; i < n; i++) {
			b[i] -= b[k] * a[i][k];
		} 
	}
	for (i = n - 1; i >= 0; i--) {
		for (j = i + 1; j < n; j++) {
			b[i] -= a[i][j] * b[j];
		} 
	}
	return true;
}