常用数学函数（pascal）

十进制转换K进制
function dectok(x,k:longint):string;
const alph='0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
var st:string;
begin
  st:='';
  while x<>0 do 
    begin
         st:=alph[x mod k+1]+st;
         x:=x div k;
       end;
  exit(st);
end;
 
K进制转换十进制
function ktodec(st:string; k:longint):longint;
const alph='012456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
var i,j,ans:longint;
begin
  ans:=0;
  j:=1;
  for i:=length(st) downto 1 do 
    begin
         inc(ans,j*(pos(st[i],alph)-1));
         j:=j*k;
       end;
  exit(ans);
end;
 
欧几里得算法

function gcd(a,b:longint):longint;
begin
  if b=0 then exit(a)
  else exit(gcd(b,a mod b));
end;
 
求最小公倍数
function lcm(a,b:longint):longint;
begin
  exit(a div gcd(a,b) *b);
end;
 
判断质数
function judgeprime(x:longint);
var i:longint;
begin
  if x=1 then exit(false);
  for i:=2 to trunc(sqrt(x)) do 
    if x mod i=0 then
         exit(false);
  exit(true);
end;
 
生成质数表
procedure makeprime;
var i,j:longint;
begin
  fillchar(f,sizeof(f),0);
  f[1]:=true;
  for i:=2 to n do