//cout<

//cout<

//cout<

#include

#include

#include

#define N 5

void main()

{

//三对角阵的Crout分解

double a[N][N]={{2,-1,0,0,0},{-1,2,-1,0,0},{0,-1,2,-1,0},{0,0,-1,2,-1},{0,0,0,-1,2}};

double f[N]={1,0,0,0,0};

double L[N][N];

double U[N][N];

double y[N];

double x[N];

int t,r=0;

for(int i=0;i

{

for(int j=0;j

{

L[i][j]=U[i][j]=0;

}

}

cout<

for(i=0;i

{

for(int j=0;j

{

cout<

}

cout<

}

/*for(i=0;i

{

for(j=0;j

{

if(i==0)

{

if(a[i][i]!=0&&a[i][i+1]!=0||a[i][j]==0)*/

for(i=0;i

{

if(i==0)

{

if(a[i][i]==0||a[i][i+1]==0)

{

cout<

break;

}

if(fabs(a[i][i])<=fabs(a[i][i+1]))

{

cout<

break;

}

}

else if(i==N-1)

{

if(a[i][i]==0||a[i][i-1]==0)

{

cout<

break;

}

if(fabs(a[i][i])<=fabs(a[i][i-1]))

{

cout<

break;

}

}

else

{

if(a[i][i]==0||a[i][i-1]==0||a[i][i+1]==0)

{

cout<

break;

}

if(fabs(a[i][i])

{

cout<

break;

}

}

t=i;

}

if(t==N-1)

{

cout<

for(i=0;i

{

if(i==0)

{

L[i][i]=a[i][i];

U[i][i+1]=a[i][i+1]/L[i][i];

U[i][i]=1;

continue;

}

if(i==N-1)

{

L[i][i-1]=L[i][i]=a[i][i]-a[i][i-1]*U[i-1][i];

U[i][i]=1;

}

else

{

L[i][i-1]=L[i][i]=a[i][i]-a[i][i-1]*U[i-1][i];

U[i][i+1]=a[i][i+1]/L[i][i];

U[i][i]=1;

}

}

cout<

for(i=0;i

{

for(int j=0;j

{

//cout<

//cout<

cout<

}

cout<

}

cout<

for(i=0;i

{

for(int j=0;j

{

cout<

}

cout<

}

y[0]=f[0]/a[0][0];//解下三角方程组

for(i=1;i

{

y[i]=(f[i]-a[i][i-1]*y[i-1])/L[i][i];

}

x[i-1]=y[i-1];//解上三角方程组

for(i=N-2;i>=0;i--)

{

x[i]=y[i]-U[i][i+1]*x[i+1];

}

cout<

for(i=0;i

{

cout<

}

cout<

}

}