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Initial data commit

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Ingy döt Net 2023-07-01 11:58:00 -04:00
parent 72d218235f
commit f23f22d71c
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68
Task/Totient-function/Pascal/totient-function-2.pas Normal file
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function totient(n:NativeUInt):NativeUInt;
const
//delta of numbers not divisible by 2,3,5 (0_1+6->7+4->11 ..+6->29+2->3_1
delta : array[0..7] of NativeUint = (6,4,2,4,2,4,6,2);
var
i, quot,idx: NativeUint;
Begin
// div mod by constant is fast.
//i = 2
result := n;
if (2*2 <= n) then
Begin
IF not(ODD(n)) then
Begin
// remove numbers with factor 2,4,8,16, ...
while not(ODD(n)) do
n := n DIV 2;
//remove count of multiples of 2
dec(result,result DIV 2);
end;
end;
//i = 3
If (3*3 <= n) AND (n mod 3 = 0) then
Begin
repeat
quot := n DIV 3;
IF n <> quot*3 then
BREAK
else
n := quot;
until false;
dec(result,result DIV 3);
end;
//i = 5
If (5*5 <= n) AND (n mod 5 = 0) then
Begin
repeat
quot := n DIV 5;
IF n <> quot*5 then
BREAK
else
n := quot;
until false;
dec(result,result DIV 5);
end;
i := 7;
idx := 1;
//i = 7,11,13,17,19,23,29, ...49 ..
while i*i <= n do
Begin
quot := n DIV i;
if n = quot*i then
Begin
repeat
IF n <> quot*i then
BREAK
else
n := quot;
quot := n DIV i;
until false;
dec(result,result DIV i);
end;
i := i + delta[idx];
idx := (idx+1) AND 7;
end;
if n> 1 then
dec(result,result div n);
end;