Regex: Alphanumeric, with at least one number and one character

alphanumeric_regex

// Match alphanumeric strings, with at least one number and one character.
// -----------------------------------------------------------------------
(               // Find a group of:
  [0-9]+[a-z]   // - one or more digits, followed by a character. 
  |             // - OR
  [a-z]+[0-9]   // - one or more characters, followed by a digit.
)
[a-z0-9]*       // Then, 0 or more digits or characters.

// Match hexadecimal strings, with at least one number and one character.
// ----------------------------------------------------------------------
(              // Find a group of:
  [0-9]+[a-f]  // - one or more digits, followed by a character.
  |            // - OR 
  [a-f]+[0-9]  // - one or more characters, followed by a digit.
)
[a-f0-9]*      // Then, 0 or more digits or characters.

// Match exactly 32 characters.
(                 // Try to match this group:
  ?=              // Look ahead for:
  .*              // 0 or more of anything
  (               // Then:
    [a-f]+[0-9]   // One or more a-f, followed by one number.
    |             // OR
    [0-9]+[a-f]   // One or more 0-9, followed by one character.
  )
)
[a-f0-9]{32}      // Exactly 32 characters, which are any of a-f or 0-9.