408. valid word abbreviation

A string can be abbreviated by replacing any number of non-adjacent, non-empty substrings with their lengths. The lengths should not have leading zeros.

For example, a string such as "substitution" could be abbreviated as (but not limited to):

• "s10n" ("s ubstitutio n")
• "sub4u4" ("sub stit u tion")
• "12" ("substitution")
• "su3i1u2on" ("su bst i t u ti on")
• "substitution" (no substrings replaced)

The following are not valid abbreviations:

• "s55n" ("s ubsti tutio n", the replaced substrings are adjacent)
• "s010n" (has leading zeros)
• "s0ubstitution" (replaces an empty substring)

Given a string word and an abbreviation abbr, return whether the string matches the given abbreviation.

A substring is a contiguous non-empty sequence of characters within a string.

solution

Iterate through the two strings.

def validWordAbbreviation(self, word: str, abbr: str) -> bool:
	word_ptr, abbr_ptr = 0, 0
 
	while abbr_ptr < len(abbr) and word_ptr < len(word):
		# check for character match
		if abbr[abbr_ptr].isalpha():
			if word[word_ptr] != abbr[abbr_ptr]:
				return False
			abbr_ptr += 1
			word_ptr += 1
 
		else:
			# parse the number
			num = int(abbr[abbr_ptr])
			if num == 0: return False
			abbr_ptr += 1
			while abbr_ptr < len(abbr) and abbr[abbr_ptr].isnumeric():
				num *= 10
				num += int(abbr[abbr_ptr])
				abbr_ptr += 1
			word_ptr += num
 
	return abbr_ptr == len(abbr) and word_ptr == len(word)