809. Expressive Words 

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class Solution {
    public int expressiveWords(String s, String[] words) {
        int expressiveWords = 0;

        for (String word : words) {
            if (match(s, word)) {
                expressiveWords++;
            }
        }

        return expressiveWords;
    }

    private boolean match(String s, String word) {
        int i = 0, j = 0;
        while (i < s.length() && j < word.length()) {
            if (s.charAt(i) != word.charAt(j)) {
                return false;
            }

            int nextI = i;
            while (nextI < s.length() && s.charAt(nextI) == s.charAt(i)) {
                nextI++;
            }
            int exceptedCount = nextI - i; // 注意此时 s[nextI] != s[i]

            int nextJ = j;
            while (nextJ < word.length() && word.charAt(nextJ) == word.charAt(j)) {
                nextJ++;
            }
            int actualCount = nextJ - j;  // 注意此时 s[nextJ] != s[j]

            if (exceptedCount < actualCount) {
                return false;
            }

            i = nextI;
            j = nextJ;

            if (exceptedCount == actualCount) {
                continue;
            }
            if (exceptedCount == 2) {
                return false;
            }
        }

        return i == s.length() && j == word.length();
    }
}

注意指针移动细节，注意 word 需要被匹配完而不仅仅是把 s 匹配完。

References

809. Expressive Words