Given a non-empty string s and an abbreviation abbr, return whether the string matches with the given abbreviation.

A string such as "word" contains only the following valid abbreviations:

["word", "1ord", "w1rd", "wo1d", "wor1", "2rd", "w2d", "wo2", "1o1d", "1or1", "w1r1", "1o2", "2r1", "3d", "w3", "4"]

Notice that only the above abbreviations are valid abbreviations of the string "word". Any other string is not a valid abbreviation of "word".

Note: Assume s contains only lowercase letters and abbr contains only lowercase letters and digits.

Example 1:
Given s = "internationalization", abbr = "i12iz4n":

Return true.
Example 2:
Given s = "apple", abbr = "a2e":

Return false.

Solution

public class Solution {
    public boolean validWordAbbreviation(String word, String abbr) {
        int i = 0;
        int j = 0;

        while(j < abbr.length()) {
            if( Character.isDigit( abbr.charAt(j)) ) {
                if(abbr.charAt(j) == '0') return false; // invalid
                int begin = j;
                while(j < abbr.length() && Character.isDigit( abbr.charAt(j) ) ) j++;
                int num = Integer.valueOf(abbr.substring(begin, j));
                i += num;
                if(i > word.length()) return false;
            } else {
                if(i == word.length() || word.charAt(i) != abbr.charAt(j)) return false;
                i++;
                j++;
            }
        }
        return i == word.length();
    }
}