CS计算机代考程序代写 A=[1 2 3 4;

A=[1 2 3 4;
3 4 8 9;
8 20 4 3;
5 6 7 8];
C=[3;4;8;10];

[L,U]=LUDecomposition(A)

R=LowerTriangularSolver(L,C)
X=UpperTriangularSolver(U,R)

function [L,U]=LUDecomposition(A)

[n,n]=size(A);
L=zeros(n,n);
U=zeros(n,n);

for i=1:n
L(i,1)=A(i,1)
end
for j=2:n
U(1,j)=A(1,j)/L(1,1)
end

for j=2:n
for i=j:n
sum=0;
for k=1:j-1
sum=sum+L(i,k)*U(k,j)
end
L(i,j)=A(i,j)-sum;
end

for k=j+1:n
sum=0;
for i=1:j-1
sum=sum+L(j,i)*U(i,k)
end
U(j,k)=(A(j,k)-sum)/L(j,j);
end
end

for i=1:n
U(i,i)=1.0;
end

end

function x=UpperTriangularSolver(A,C)
[n,n]=size(A) % Finding the size of the problem
x=zeros(n,1) % set up x vector with elements initially set to zero
x(n)=C(n)/A(n,n);
for i=n-1:-1:1
sum=0;
for j=i+1:n
sum=sum+A(i,j)*x(j);
end
x(i)=(C(i)-sum)/A(i,i);
end
end

function x=LowerTriangularSolver(A,C)
[n,n]=size(A); % Finding the size of the problem
x=zeros(n,1); % set up x vector with elements initially set to zero
x(1)=C(1)/A(1,1);
for i=2:n
sum=0;
for j=1:i-1
sum=sum+A(i,j)*x(j);
end
x(i)=(C(i)-sum)/A(i,i);
end
end