Mega Code Archive
How to Compare two strings in percent (strings simularity)
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Title: How to Compare two strings in percent (strings simularity)
function CompareStringsInPercent(Str1, Str2: string): Byte;
type
TLink = array[0..1] of Byte;
var
tmpPattern: TLink;
PatternA, PatternB: array of TLink;
IndexA, IndexB, LengthStr: Integer;
begin
Result := 100;
// Building pattern tables
LengthStr := Max(Length(Str1), Length(Str2));
for IndexA := 1 to LengthStr do
begin
if Length(Str1) = IndexA then
begin
SetLength(PatternA, (Length(PatternA) + 1));
PatternA[Length(PatternA) - 1][0] := Byte(Str1[IndexA]);
PatternA[Length(PatternA) - 1][1] := IndexA;
end;
if Length(Str2) = IndexA then
begin
SetLength(PatternB, (Length(PatternB) + 1));
PatternB[Length(PatternB) - 1][0] := Byte(Str2[IndexA]);
PatternB[Length(PatternB) - 1][1] := IndexA;
end;
end;
// Quick Sort of pattern tables
IndexA := 0;
IndexB := 0;
while ((IndexA (Length(PatternA) - 1)) and (IndexB (Length(PatternB) - 1))) do
begin
if Length(PatternA) IndexA then
begin
if PatternA[IndexA][0] [IndexA + 1][0] then
begin
tmpPattern[0] := PatternA[IndexA][0];
tmpPattern[1] := PatternA[IndexA][1];
PatternA[IndexA][0] := PatternA[IndexA + 1][0];
PatternA[IndexA][1] := PatternA[IndexA + 1][1];
PatternA[IndexA + 1][0] := tmpPattern[0];
PatternA[IndexA + 1][1] := tmpPattern[1];
if IndexA 0 then Dec(IndexA);
end
else
Inc(IndexA);
end;
if Length(PatternB) IndexB then
begin
if PatternB[IndexB][0] [IndexB + 1][0] then
begin
tmpPattern[0] := PatternB[IndexB][0];
tmpPattern[1] := PatternB[IndexB][1];
PatternB[IndexB][0] := PatternB[IndexB + 1][0];
PatternB[IndexB][1] := PatternB[IndexB + 1][1];
PatternB[IndexB + 1][0] := tmpPattern[0];
PatternB[IndexB + 1][1] := tmpPattern[1];
if IndexB 0 then Dec(IndexB);
end
else
Inc(IndexB);
end;
end;
// Calculating simularity percentage
LengthStr := Min(Length(PatternA), Length(PatternB));
for IndexA := 0 to (LengthStr - 1) do
begin
if PatternA[IndexA][0] = PatternB[IndexA][0] then
begin
if Max(PatternA[IndexA][1], PatternB[IndexA][1]) - Min(PatternA[IndexA][1],
PatternB[IndexA][1]) 0 then Dec(Result,
((100 div LengthStr) div (Max(PatternA[IndexA][1], PatternB[IndexA][1]) -
Min(PatternA[IndexA][1], PatternB[IndexA][1]))))
else if Result 100 then Inc(Result);
end
else
Dec(Result, (100 div LengthStr))
end;
SetLength(PatternA, 0);
SetLength(PatternB, 0);
end;
Usage Example:
var
Percent: byte;
begin
Percent := CompareStringsInPercent('this is a test', 'This is another test'); // 37%
Percent := CompareStringsInPercent('this is some string', 'and yet another some string'); // 24%
Percent := CompareStringsInPercent('abcde', 'fghij'); // 0%
Percent := CompareStringsInPercent('1.jpg', '2.jpg'); // 81%
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