Cách khởi tạo Bignum:
type bignum = array [0..maxn] of word;
var xs,ys:ansistring;
x,y,z:bignum;
i,j,dem,max:longint;
begin
readln(xs);
readln(ys);
fillchar(x,sizeof(x),0);
fillchar(y,sizeof(y),0);
x[0]:=length(xs);
y[0]:=length(ys);
for i:=x[0] downto 1 do
begin x[x[0]-i+1]:= ord(xs[i])-48; end;
for j:=y[0] downto 1 do
begin y[y[0]-j+1]:= ord(xs[j])-48; end;
end.
Ý tưởng: a x b = a + a + a ... a (b lần)
(mình chỉ có sẵn thuật toán cộng số lớn, còn lại bạn tự viết nha)
const maxn=1000;
type bignum = array [0..maxn] of word;
var xs,ys:ansistring;
x,y,z:bignum;
i,j,dem,max:longint;
begin
readln(xs);
readln(ys);
fillchar(x,sizeof(x),0);
fillchar(y,sizeof(y),0);
fillchar(z,sizeof(z),0);
x[0]:=length(xs);
y[0]:=length(ys);
for i:=x[0] downto 1 do
begin x[x[0]-i+1]:= ord(xs[i])-48; end;
for j:=y[0] downto 1 do
begin y[y[0]-j+1]:= ord(xs[j])-48; end;
dem:=0;
if x[0] > y[0] then max:= x[0] else max:=y[0];
for i:=1 to max do
begin
z[i]:=(x[i]+y[i]+dem) mod 10;
dem:=(x[i]+y[i]+dem) div 10;
end;
if dem >0 then
begin
inc(z[0]);
z[z[0]]:=dem;
end;
for i:=max downto 1 do
write(z[i]);
end.
