program MinimumDistanceProgram;
{$mode objfpc}{$H+}
uses
SysUtils;
type
TIntArray = array of Integer;
{
Finds the minimum distance between two target values in an array.
Parameters:
Numbers - Input array.
Target1 - First target value.
Target2 - Second target value.
Returns:
The minimum distance between the target values,
or -1 if no valid pair exists.
Time Complexity: O(n)
Space Complexity: O(1)
}
function FindMinimumDistance(
const Numbers: TIntArray;
const Target1, Target2: Integer): Integer;
var
CurrentIndex: Integer;
LastSeenIndex: Integer;
MinDistance: Integer;
begin
{ Special case: both targets are the same value }
if Target1 = Target2 then
begin
LastSeenIndex := -1;
MinDistance := MaxInt;
for CurrentIndex := Low(Numbers) to High(Numbers) do
begin
if Numbers[CurrentIndex] <> Target1 then
Continue;
if (LastSeenIndex <> -1) and
(Numbers[CurrentIndex] <> Numbers[LastSeenIndex]) then
begin
if (CurrentIndex - LastSeenIndex) < MinDistance then
MinDistance := CurrentIndex - LastSeenIndex;
end;
LastSeenIndex := CurrentIndex;
end;
if MinDistance = MaxInt then
Exit(-1);
Exit(MinDistance);
end;
LastSeenIndex := -1;
MinDistance := MaxInt;
for CurrentIndex := Low(Numbers) to High(Numbers) do
begin
{ Skip values that are not targets }
if (Numbers[CurrentIndex] <> Target1) and
(Numbers[CurrentIndex] <> Target2) then
Continue;
{
If we previously encountered one target value and
the current value is the other target value,
update the minimum distance.
}
if (LastSeenIndex <> -1) and
(Numbers[CurrentIndex] <> Numbers[LastSeenIndex]) then
begin
if (CurrentIndex - LastSeenIndex) < MinDistance then
MinDistance := CurrentIndex - LastSeenIndex;
end;
{ Remember the most recent occurrence }
LastSeenIndex := CurrentIndex;
end;
if MinDistance = MaxInt then
Result := -1
else
Result := MinDistance;
end;
var
Numbers: TIntArray;
Distance: Integer;
begin
Numbers := TIntArray.Create(2, 3, 7, 3, 3, 4, 8, 8, 8, 11, 9, 1, 3);
Distance := FindMinimumDistance(Numbers, 3, 8);
if Distance >= 0 then
WriteLn('Minimum distance between 3 and 8: ', Distance)
else
WriteLn('No valid pair found.');
end.
{
run:
Minimum distance between 3 and 8: 2
}
