看来没有说清楚，计算行列式我当然会，我要的是具体到c++上应该怎么算，能否给段代码出来

学高代时就有体会：不断的重复那么一件事！
乘完加，加完乘的，化三角呗！

[此贴子已经被作者于2007-9-29 22:37:08编辑过]

see http://en.wikipedia.org/wiki/Determinant

As far as I know, there are at least 3 methods:

0. Leibniz formula --- calculate all n! products and sum them up;
1. Recur on minors;
2. Gaussian elimination.

/*---------------------------------------------------------------------------
File name: determinant.c
Author: HJin (email: fish_sea_bird [at] yahoo [dot] com )
Created on: 10/29/2007 20:38:40
Environment: WinXPSP2 En Pro + VS2005 v8.0.50727.762

use the uppper-triangulation process to calculate the
determinant of a matrix.
*/

#include <stdio.h>
#include <math.h>

#define N 3
#define EPS 1e-10

void PrintMatrix(double a[][N])
{
int i, j;

for (i = 0; i < N; ++i)
{
for (j = 0; j < N; ++j)
{
printf("%8.4g ", a[i][j]);
}
printf("\n");
}
printf("\n");
}

/*
* divides a row of a by the divisor. divisor != 0.0.
*/
void DivideRow(double a[][N], int r, double divisor)
{
int j;

for (j = 0; j < N; ++j)
{
a[r][j] /= divisor;
}
}

/*
* row1 := row 1 - row2.
*/
void SubtractRow(double a[][N], int r1, int r2)
{
int j;
for (j = 0; j < N; ++j)
{
a[r1][j] -= a[r2][j];
}
}

/*
* Upper-triangulates a matrix.
* returns the determinant of the matrix.
*/
double LU(double a[][N])
{
int i, j, k;
double factor = 1.0;
double temp;

// skip row 0
for (i = 1; i < N; ++i)
{
for (j = 0; j < i; ++j)
{
if (i != j)
{
temp = a[i][j];
if (fabs(temp) > EPS)
{
DivideRow(a, i, temp);
factor *= temp;
}
}

temp = a[j][j];
if (fabs(temp) > EPS && fabs(temp - 1.0) > EPS)
{
DivideRow(a, j, temp);
factor *= temp;
}

if (fabs(a[i][j]) > EPS)
{
SubtractRow(a, i, j);
}

for (k = 0; k < N; ++k)
{
if (fabs(a[k][k]) <= EPS)
{
return 0.0;
}
}
}
}

a[N-1][N-1] *= factor;

return a[N-1][N-1];
}

double multDia(double a[][N])
{
int i;
double factor = 1.0;

for (i = 0; i < N; ++i)
{
factor *= a[i][i];
}
return factor;
}

int main()
{
double a[N][N] =
{
{8, 0, 1},
{2, 1, 3},
{5, 3, 9}
};
double factor;

PrintMatrix(a);
factor = LU(a);
PrintMatrix(a);

printf("determinant = %g.\n", factor);

return 0;
}