Initial data commit

Task/Successive-prime-differences/Delphi/successive-prime-differences.delphi

@@ -0,0 +1,147 @@
+program Successive_prime_differences;
+
+
+{$APPTYPE CONSOLE}
+
+{$R *.res}
+
+uses
+  System.SysUtils,
+  System.Generics.Collections;
+
+function IsPrime(a: UInt64): Boolean;
+var
+  d: UInt64;
+begin
+  if (a < 2) then
+    exit(False);
+
+  if (a mod 2) = 0 then
+    exit(a = 2);
+
+  if (a mod 3) = 0 then
+    exit(a = 3);
+
+  d := 5;
+
+  while (d * d <= a) do
+  begin
+    if (a mod d = 0) then
+      Exit(false);
+    inc(d, 2);
+
+    if (a mod d = 0) then
+      Exit(false);
+    inc(d, 4);
+  end;
+
+  Result := True;
+end;
+
+function Primes(const limit: UInt64): TArray<UInt64>;
+var
+  i: UInt64;
+
+  procedure Add(const value: UInt64);
+  begin
+    SetLength(result, Length(result) + 1);
+    Result[Length(result) - 1] := value;
+  end;
+
+begin
+  if limit < 2 then
+    exit;
+
+  // 2 is the only even prime
+  Add(2);
+
+  i := 3;
+  while i <= limit do
+  begin
+    if IsPrime(i) then
+      Add(i);
+    inc(i, 2);
+  end;
+end;
+
+function Commatize(const n: UInt64): string;
+var
+  str: string;
+  digits: Integer;
+  i: Integer;
+begin
+  Result := '';
+  str := n.ToString;
+  digits := str.Length;
+
+  for i := 1 to digits do
+  begin
+    if ((i > 1) and (((i - 1) mod 3) = (digits mod 3))) then
+      Result := Result + ',';
+    Result := Result + str[i];
+  end;
+end;
+
+function CheckScan(index: Integer; p: TArray<UInt64>; pattern: array of Integer): Boolean;
+var
+  i, last: Integer;
+begin
+  last := Length(pattern) - 1;
+  for i := 0 to last do
+    if p[index - last + i - 1] + pattern[i] <> p[index - last + i] then
+      exit(False);
+  Result := True;
+end;
+
+const
+  GroupLabel: array[1..6] of string = ('(2)', '(1)', '(2, 2)', '(2, 4)',
+    '(4, 2)', '(6, 4, 2)');
+
+var
+  limit, start: UInt64;
+  c: TArray<UInt64>;
+  i, j: UInt64;
+  Group: array[1..6] of Tlist<string>;
+
+begin
+  for i := 1 to 6 do
+    Group[i] := Tlist<string>.Create;
+
+  limit := Trunc(1e6 - 1);
+  c := Primes(limit);
+
+  for j := 1 to High(c) do
+  begin
+    if CheckScan(j, c, [2]) then
+      Group[1].Add(format('(%d,%d)', [c[j - 1], c[j]]));
+
+    if CheckScan(j, c, [1]) then
+      Group[2].Add(format('(%d,%d)', [c[j - 1], c[j]]));
+
+    if j > 1 then
+    begin
+      if CheckScan(j, c, [2, 2]) then
+        Group[3].Add(format('(%d,%d,%d)', [c[j - 2], c[j - 1], c[j]]));
+
+      if CheckScan(j, c, [2, 4]) then
+        Group[4].Add(format('(%d,%d,%d)', [c[j - 2], c[j - 1], c[j]]));
+
+      if CheckScan(j, c, [4, 2]) then
+        Group[5].Add(format('(%d,%d,%d)', [c[j - 2], c[j - 1], c[j]]));
+    end;
+
+    if j > 2 then
+      if CheckScan(j, c, [6, 4, 2]) then
+        Group[6].Add(format('(%d,%d,%d,%d)', [c[j - 3], c[j - 2], c[j - 1], c[j]]));
+
+  end;
+
+  for i := 1 to 6 do
+  begin
+    Write(GroupLabel[i], ': first group = ', Group[i].First);
+    Writeln(', last group = ', Group[i].last, ', count = ', Group[i].Count);
+    Group[i].free;
+  end;
+
+  readln;
+end.