//利用高斯顺序消元法,得到上三角阵
void GaussElimination_Sequence(vector<vector<double>> &a, int n, vector<double> &b)
{
int i, k, j;
double t;
//k表示用来消元的行号,从第0行到第n-1行
for (k = 0; k <= n - 1; k++)
{
//用第k行,对第i行进行消元,i的范围:[k+1,n-1]
for (i = k + 1; i < n; i++)
{
t = a[i][k] / a[k][k];
for (j = k; j < n; j++)
{
a[i][j] = a[i][j] - t * a[k][j];
}
b[i] = b[i] - t * b[k];
}
}
}
double A[4][4];
double X[4];
double b[4];
GaussElimination_Sequence(A[4][4], 4, b[4]); //这个地方要怎么改?