Решения СЛАУ методом Гаусса

TYPE MAT=ARRAY [1..20,1..21] OF REAL;
     VEC=ARRAY [1..20] OF REAL;
VAR A:MAT;
    X:VEC;
    I,N:INTEGER;
    S:REAL;
PROCEDURE MATR (N:INTEGER; VAR A:MAT);
VAR I,J:INTEGER;
BEGIN FOR I:=1 TO N DO
      FOR J:=1 TO N+1 DO BEGIN
      WRITE ('A',I:2,J:2,'?'); READLN (A[I,J])
      END
END;
PROCEDURE GAUSS (N:INTEGER; VAR A:MAT; VAR X:VEC; VAR S:REAL);
VAR I,J,K,L,K1,N1:INTEGER;
    R:REAL;
BEGIN N1:=N+1;
      FOR K:=1 TO N DO BEGIN K1:=K+1; S:=A[K,K]; J:=K;
          FOR I:=K1 TO N DO BEGIN R:=A[I,K];
              IF ABS(R)>ABS(S) THEN BEGIN S:=R; J:=I END
          END;
          IF J<>K THEN FOR I:=K TO N1 DO BEGIN
             R:=A[K,I]; A[K,I]:=A[J,I]; A[J,I]:=R END;
          FOR J:=K1 TO N1 DO A[K,J]:=A[K,J]/S;
          FOR I:=K1 TO N DO BEGIN R:=A[I,K];
              FOR J:=K1 TO N1 DO A[I,J]:=A[I,J]-A[K,J]*R
          END
      END;
      IF S<>0.0 THEN
         FOR I:=N DOWNTO 1 DO BEGIN S:=A[I,N1];
             FOR J:=I+1 TO N DO S:=S-A[I,J]*X[J];
             X[I]:=S
         END
      END;
      BEGIN
           REPEAT WRITE ('N?'); READLN(N); MATR(N,A); GAUSS(N,A,X,S);
                  IF S<>0.0 THEN FOR I:=1 TO N DO WRITELN ('X',I:2,'=',X[I])
                     ELSE WRITELN('DET=0')
      UNTIL FALSE
      END.

TYPE MAT=ARRAY [1..10,1..20] OF REAL;
VAR I,J,N:INTEGER; S:REAL; A:MAT;
PROCEDURE MATR(N:INTEGER; VAR A:MAT);
VAR I,J:INTEGER;
BEGIN
  FOR I:=1 TO N DO
  FOR J:=1 TO N DO BEGIN
    WRITE('A',I:2,J:2,'? '); READLN(A[I,J])
  END
END;
PROCEDURE INV(N:INTEGER; VAR A:MAT; VAR S:REAL);
VAR I,J,K:INTEGER; R:REAL;
BEGIN
  FOR I:=1 TO N DO BEGIN
    FOR J:=N+1 TO 2*N DO A[I,J]:=0.0; A[I,I+N]:=1.0
  END;
  FOR K:=1 TO N DO BEGIN S:=A[K,K]; J:=K;
    FOR I:=K+1 TO N DO BEGIN R:=A[I,K];
      IF ABS(R)>ABS(S) THEN BEGIN S:=R; J:=I END
    END;
    IF S=0.0 THEN EXIT;
    IF J<>K THEN FOR I:=K TO 2*N DO BEGIN
      R:=A[K,I]; A[K,I]:=A[J,I]; A[J,I]:=R END;
    FOR J:=K+1 TO 2*N DO A[K,J]:=A[K,J]/S;
    FOR I:=K+1 TO N DO BEGIN R:=A[I,K];
      FOR J:=K+1 TO 2*N DO A[I,J]:=A[I,J]-A[K,J]*R
    END
  END;
  IF S<>0.0 THEN
    FOR J:=N-1 DOWNTO 1 DO BEGIN R:=A[I,J];
      FOR K:=I+1 TO N DO R:=R-A[K,J]*A[I,K];
      A[I,J]:=R
    END
END;
BEGIN
  REPEAT WRITE('N? '); READLN(N); MATR(N,A); INV(N,A,S);
    IF S<>0.0 THEN FOR I:=1 TO N DO
      FOR J:=N+1 TO 2*N DO WRITELN('A',I:2,J-N:2,'=',A[I,J])
      ELSE WRITELN ('DET=O')
  UNTIL FALSE
END.