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.

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Example 1:

Input: word = "internationalization", abbr = "i12iz4n"
Output: true
Explanation: The word "internationalization" can be abbreviated as "i12iz4n" ("i nternational iz atio n").

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Example 2:

Input: word = "apple", abbr = "a2e"
Output: false
Explanation: The word "apple" cannot be abbreviated as "a2e".

Constraints:

  • 1 <= word.length <= 20
  • word consists of only lowercase English letters.
  • 1 <= abbr.length <= 10
  • abbr consists of lowercase English letters and digits.
  • All the integers in abbr will fit in a 32-bit integer.

Solution Iterative + Recursive

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class Solution {
    public boolean validWordAbbreviation(String word, String abbr) {
        int i = 0;
        int j = 0;
        
        while (i < word.length() && j < abbr.length()) {
            if (word.charAt(i) == abbr.charAt(j)) {
                i++;
                j++;
                continue;
            }
            
            if (!Character.isDigit(abbr.charAt(j))) {
                return false;
            }
            
            int start = j;
            
            while (j < abbr.length() && Character.isDigit(abbr.charAt(j))) {
                j++;
            }
            
            int num = Integer.parseInt(abbr.substring(start, j));
            i += num;
        }
        
        return i == word.length() && j == abbr.length();
    }
}