Extract numbers from string (Regex C++)

Question

let\'s say i hve a string S = \"1 this is a number=200; Val+54 4class find57\"

i want to use Regex to extract only this numbers:

Answer 1

Just use word boundaries. \b matches between a word character and a non-word character.

\b\d+\b

OR

\b[0-9]+\b

DEMO

Escape the backslash one more time if necessary like \\b\\d+\\b or \\b[0-9]+\\b