簡介
所謂H數是指該數除1以外，最多只有2,3,5,7四種因子。如630是H數，而22不是。
判斷方法
用FreeBASIC來實現H數的算法
DECLARE FUNCTION HNUM(X AS INTEGER) AS INTEGER
DIM AS INTEGER I,N,J
INPUT N
I=1 'H數
J=0 '第J個H數
DO
I=I+1
IF HNUM(I)=1 THEN J=J+1
LOOP WHILE J<N
PRINT I
SLEEP
END
FUNCTION HNUM(X AS INTEGER) AS INTEGER '判斷X是否為H數，是H數並返回值1
IF X<>1 THEN
WHILE X MOD 2=0
X=X/2
WEND
WHILE X MOD 3=0
X=X/3
WEND
WHILE X MOD 5=0
X=X/5
WEND
WHILE X MOD 7=0
X=X/7
WEND
END IF
IF X=1 THEN HNUM=1
END FUNCTION
用FreePascal來實現H數的算法
var j,i,n:longint;
function sb(l:qword):boolean;
begin
sb:=false;
if l<>1
then
begin
while l mod 2=0 do l:=l div 2;
while l mod 3=0 do l:=l div 3;
while l mod 5=0 do l:=l div 5;
while l mod 7=0 do l:=l div 7;
if l=1 then sb:=true;
end;
end;
begin
read(n);
repeat
inc(i);
if sb(i) then inc(j);
until j=n;
write(i);
end.
計算方法
用FreePascal來實現求第n個H數的算法
const maxn=2147483647;
var
flag:boolean;
n,i,left,right:longint;
x:int64;
a:array[0..10000]of int64;
procedure sort(l,r: longint);
var
i,j,x,y: longint;
begin
i:=l;
j:=r;
x:=a[(l+r) div 2];
repeat
while a[i]<x do
inc(i);
while x<a[j] do
dec(j);
if not(i>j) then
begin
y:=a[i];
a[i]:=a[j];
a[j]:=y;
inc(i);
j:=j-1;
end;
until i>j;
if l<j then
sort(l,j);
if i<r then
sort(i,r);
end;
begin
a[1]:=1;
left:=1;right:=1;
while left<=right do
begin
x:=a[left]*2;
if x<=maxn
then
begin
flag:=true;
for i:=1 to right do
if a[i]=x then begin flag:=false;break;end;
if flag
then
begin
inc(right);
a[right]:=x;
end;
end;
x:=a[left]*3;
if x<=maxn
then
begin
flag:=true;
for i:=1 to right do
if a[i]=x then begin flag:=false;break;end;
if flag
then
begin
inc(right);
a[right]:=x;
end;
end;
x:=a[left]*5;
if x<=maxn
then
begin
flag:=true;
for i:=1 to right do
if a[i]=x then begin flag:=false;break;end;
if flag
then
begin
inc(right);
a[right]:=x;
end;
end;
x:=a[left]*7;
if x<=maxn
then
begin
flag:=true;
for i:=1 to right do
if a[i]=x then begin flag:=false;break;end;
if flag
then
begin
inc(right);
a[right]:=x;
end;
end;
inc(left);
end;
sort(1,right);
readln(n);
writeln(a[n]);
end.
