高斯消元

#include<iostream>
#include<math.h>
using namespace std;
#define MAXN 100
#define fabs(x) ((x)>0?(x):-(x))
#define 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
int gauss_cpivot(int m,int n, double **a, double b[])
//m,n为系数矩阵的行列，a[][]系数矩阵
//b[]常数列向量，将解x[]存入b[]中
{
    int i, j, k, row;
    double maxp, t;
    for (k = 0; k<n; k++) {
        for (maxp = 0, i = k; i<m; i++)
            if (fabs(a[i][k])>fabs(maxp))
                maxp = a[row = i][k];
        if (fabs(maxp)<eps)
            return 0;
        if (row != k) {
            for (j = k; j<n; j++)
                t = a[k][j], a[k][j] = a[row][j], a[row][j] = t;
            t = b[k], b[k] = b[row], b[row] = t;
        }
        for (j = k + 1; j<n; j++) {
            a[k][j] /= maxp;
            for (i = k + 1; i<m; i++)
                a[i][j] -= a[i][k] * a[k][j];
        }
        b[k] /= maxp;
        for (i = k + 1; i<m; i++)
            b[i] -= b[k] * a[i][k];
    }
    for (i = m - 1; i >= 0; i--)
        for (j = i + 1; j<n; j++)
            b[i] -= a[i][j] * b[j];
    return 1;
}
void main()
{
    int r, c,i,j;
    double **a, *b;
    cin >> r >> c;
    a = new double*[r];
    for (i = 0; i < r; i++)
        a[i] = new double[c];
    b = new double[r];
    for (i = 0; i < r; i++)
    {
        b[i] = rand();
        for (j = 0; j < c; j++)
            a[i][j] = rand();
    }
    gauss_cpivot(r,c, a, b);
    for (i = 0; i < r; i++)
        cout << b[i] << endl;
}