Author: Lou Adler

How to get the number of occurrences of a substring within a string 

Answer:

Answer 1:

I don't know of any existing code in Delphi to do this. If performance isn't 
critical you can always use brute force. The following works but can easily be 
improved:

1   function CountSubString(SubStr, St: string): integer;
2   var
3     i: integer;
4   begin
5     Result := 0;
6     for i := 1 to Length(st) do
7       if (copy(st, i, length(SubStr)) = SubStr) then
8         inc(Result);
9   end;



Answer 2:

While you can fiddle with the pos function and truncating the containing string 
after each "find," I think the brute force method is easiest to code (untested):

10  function SubstrCount(sub, container: string): integer;
11  var
12    index: integer;
13  begin
14    result := 0;
15    for index := 1 to (length(container) - length(sub) + 1) do
16      if copy(container, index, length(sub)) = sub then
17        inc(result);
18  end;


If you need to skip over the found substring, say to count two occurrences of "AA" 
within "AAAA" instead of three, change to:

19  function SubstrCount(sub, container: string): integer;
20  var
21    index: integer;
22  begin
23    result := 0;
24    index := 1;
25    while index <= (length(container) - length(sub) + 1) do
26    begin
27      if copy(container, index, length(sub)) = sub then
28      begin
29        inc(result);
30        index := index + length(sub);
31      end
32      else
33        inc(index);
34    end;
35  end;



Answer 3:

36  function SubStringCount(const str, substr: string): Integer;
37  var
38    start: integer;
39  begin
40    result := 0;
41    start := 0;
42    repeat
43      start := posex(substr, str, start + 1);
44      if (start = 0) then
45        break
46      else
47        inc(Result);
48    until
49      false;
50  end;