LeetCode [408] Valid Word Abbreviation

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.

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class Solution { public: bool validWordAbbreviation(string word, string abbr) { int i = 0, j = 0, sw = word.size(), sa = abbr.size(); while(i<sw && j<sa){ if(word[i]==abbr[j]) { i++; j++; } else{ if(!isdigit(abbr[j])||abbr[j]=='0') return false; int k = j; while(k<sa && isdigit(abbr[k])) k++; int cnt = stoi(abbr.substr(j, k-j)); j = k; i += cnt; } } return (i==sw && j==sa); } };