gaussex.cpp

gauss消去法的Ｃ＋＋程序

#include "iostream.h"
#include <string.h>

void main()
{
	int i = 0, j = 0; 

	int k = 0, n = 0;
	double a[][5] = {{2,9,9,7,4},{2,4,3,7,9},{6,1,2,5,5},{7,4,2,8,3}};
	double b1[5], m[4][5];
	memset(b1,0,sizeof(b1));
	memset(m,0,sizeof(m));
	cout<<"a=\n";
	for( i = 0; i < 4; i++)
	{
		for(j = 0; j < 5; j++)
		{
			cout<<a[i][j]<<"\t";
		}
		cout<<"\n";
	}
	for(k = 0; k < 4; k ++)
	{
		
		int m1 = 0, m2 = 0;
		for(i = k; i < 4; i ++)
		{
			if(a[i][k] > a[i+1][k]) m1 = i;			     
		}		
		for(j = 0; j < 5; j ++)		
			{
				b1[j] = a[k][j];
				a[k][j] = a[m1][j];
				a[m1][j] = b1[j];
			}

		for(i = k + 1; i < 4; i ++)			
		{
			m[i][k] = a[i][k]/a[k][k];
			for(j = k ; j < 5; j ++)
			{
				a[i][j] = a[i][j] - m[i][k]*a[k][j];
			}
		}
	}
	cout<<"a=\n";
	for( i = 0; i < 4; i++)
	{
		for(j = 0; j < 5; j++)
		{
			cout<<a[i][j]<<"\t";
		}
		cout<<"\n";
	}
	double x[4] = {0,0,0,0};		
	x[3] = a[3][4]/a[3][3];
	double sum = 0;
		for(k = 2; k >= 0; k--)		
	{
		double b[4] = {0,0,0};
		double sum = 0;
		for(j = k ; j < 4; j++)
		{
			sum += a[k][j+1]*x[j+1];
		}
		x[k] = (a[k][4] - sum) / a[k][k];
	}

	for(i = 0; i < 4; i++)
		cout<<"\nx["<<i<<"]="<<x[i];
}