INVERSAT.txt
program inversa_di_una_matrice_triangolare_superiore;
(* questo programma inverte una matrice triangolare superiore *)
uses crt,dos;
label 100;
var i,j,p,n:integer;
A,B:array[1..20,1..20] of real;
s:real;
h:char;
begin
clrscr;
writeln('introduci n :');
readln(n);
writeln;
for i:=1 to n do
begin
for j:=i to n do
begin
writeln(' introduci il valore di posto : ',i,' ',j);
readln(A[i,j]);
if (A[i,i]=0) then
begin
writeln;
writeln(' matrice non invertibile ');
goto 100;
end;
end;
end;
for i:=1 to n do
begin
for j:=1 to (i-1) do
begin
A[i,j]:=0;
end;
end;
writeln;
writeln('visualizzo la matrice triangolare da invertire :');
for i:=1 to n do
begin
writeln;
for j:=1 to n do
begin
write(' ',A[i,j]:0:2);
end;
end;
writeln;
(*ora passo ad invertire la matrice*)
for j:=1 to n do
begin
B[j,j]:=1/A[j,j];
for i:=(j-1) downto 1 do
begin
s:=0;
for p:=n downto (i+1) do
begin
s:=s-A[i,p]*B[p,j];
end;
B[i,j]:=s/A[i,i];
end;
end;
for i:=1 to n do
begin
for j:=1 to (i-1) do
begin
B[i,j]:=0;
(* la matrice B e' anch'essa triangolare superiore *)
Pagina 1
INVERSAT.txt
end;
end;
writeln;
writeln('la matrice inversa di A e'' :');
for i:=1 to n do
begin
writeln;
for j:=1 to n do
begin
write(' ',B[i,j]:0:2);
end;
end;
100: writeln;
writeln;
writeln(' premi un tasto per tornare all''edit :');
readln(h);
end.
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