program CountryLookup;
{$mode objfpc}{$H+}
uses
SysUtils;
type
{------------------------------------------------------------
TCountryEntry
Represents a single ISO alpha‑2 → country name mapping.
------------------------------------------------------------}
TCountryEntry = record
Code: string[2];
Name: string;
end;
{------------------------------------------------------------
A sorted lookup table for fast binary search.
Add more entries as needed, but keep it sorted by Code.
------------------------------------------------------------}
const
CountryTable: array[0..8] of TCountryEntry = (
(Code: 'CA'; Name: 'Canada'),
(Code: 'CN'; Name: 'China'),
(Code: 'DE'; Name: 'Germany'),
(Code: 'FR'; Name: 'France'),
(Code: 'GB'; Name: 'United Kingdom'),
(Code: 'KR'; Name: 'South Korea'),
(Code: 'IN'; Name: 'India'),
(Code: 'JP'; Name: 'Japan'),
(Code: 'US'; Name: 'United States')
);
CountryCount = Length(CountryTable);
{------------------------------------------------------------
NormalizeCode
Converts a 2‑letter code to uppercase for consistent matching.
------------------------------------------------------------}
function NormalizeCode(const S: string): string;
begin
Result := UpperCase(Trim(S));
end;
{------------------------------------------------------------
GetCountryName
Performs a binary search on the sorted table.
Returns an empty string if the code is not found.
------------------------------------------------------------}
function GetCountryName(const Alpha2: string): string;
var
Code: string;
Left, Right, Mid: Integer;
Cmp: Integer;
begin
Code := NormalizeCode(Alpha2);
Left := 0;
Right := CountryCount - 1;
while Left <= Right do
begin
Mid := (Left + Right) div 2;
Cmp := CompareStr(Code, CountryTable[Mid].Code);
if Cmp = 0 then
begin
Result := CountryTable[Mid].Name;
Exit;
end
else if Cmp < 0 then
Right := Mid - 1
else
Left := Mid + 1;
end;
Result := ''; { Not found }
end;
{------------------------------------------------------------
Main
Demonstrates the lookup function with several sample codes.
------------------------------------------------------------}
var
Codes: array[0..4] of string = ('US', 'GB', 'FR', 'JP', 'ZZ');
I: Integer;
Name: string;
begin
for I := 0 to High(Codes) do
begin
Name := GetCountryName(Codes[I]);
if Name <> '' then
WriteLn(Codes[I], ' → ', Name)
else
WriteLn(Codes[I], ' → (invalid code)');
end;
end.
{
run:
US → United States
GB → United Kingdom
FR → France
JP → Japan
ZZ → (invalid code)
}
