Bài 1:

uses crt;
var a,b:array[1..99]of integer;
i,n,dem,dem1,d:integer;
st:string;
begin
clrscr;
write('n='); readln(n);
for i:=1 to n do
begin
write('a[',i,']='); readln(a[i]);
end;
{---------------------------------xu-ly----------------------------------}
dem:=0;
dem1:=0;
for i:=1 to n do
if a[i]>0 then
begin
str(a[i],st);
d:=length(st);
if d=3 then
begin
inc(dem);
inc(dem1);
b[dem1]:=a[i];
end;
end;
writeln('co ',dem,' so duong co 3 chu so trong day');
writeln('cac so do la: ');
for i:=1 to dem1 do
write(b[i]:4);
readln;
end.

Bài 2:

uses crt;
var st:string;
dem,d,i:integer;
begin
clrscr;
write('nhap xau ki tu:'); readln(st);
d:=length(st);
dem:=0;
for i:=1 to d do
if st[i]='1' then inc(dem);
writeln('trong xau co ',dem,' ki tu chu so 1');
readln;
end.

Uses crt;
Var st:string;
dem,d,i:integer;
Begin
Clrscr;
write('nhap so:'); readln(st);
d:=length(st);
dem:=0;
for i:=1 to d do
if st[i]='1' then inc(dem);
Writeln('so ky tu so: ',dem,' ki tu chu so 1');
Readln;
End.