lubksb.cpp

来自「C++数值算法原书代码」· C++ 代码 · 共 25 行

#include "nr.h"

void NR::lubksb(Mat_I_DP &a, Vec_I_INT &indx, Vec_IO_DP &b)
{
	int i,ii=0,ip,j;
	DP sum;

	int n=a.nrows();
	for (i=0;i<n;i++) {
		ip=indx[i];
		sum=b[ip];
		b[ip]=b[i];
		if (ii != 0)
			for (j=ii-1;j<i;j++) sum -= a[i][j]*b[j];
		else if (sum != 0.0)
			ii=i+1;
		b[i]=sum;
	}
	for (i=n-1;i>=0;i--) {
		sum=b[i];
		for (j=i+1;j<n;j++) sum -= a[i][j]*b[j];
		b[i]=sum/a[i][i];
	}
}