Add Bold Tag in String

You are given a string s and an array of strings words.

You should add a closed pair of bold tag <b> and </b> to wrap the substrings in s that exist in words.

• If two such substrings overlap, you should wrap them together with only one pair of closed bold-tag.
• If two substrings wrapped by bold tags are consecutive, you should combine them.

Return s after adding the bold tags.

Example 1:

Input: s = "abcxyz123", words = ["abc","123"]

Output: "<b>abc</b>xyz<b>123</b>"

Explanation: The two strings of words are substrings of s as following: "abcxyz123".
We add before each substring and after each substring.

Example 2:

Input: s = "aaabbb", words = ["aa","b"]

Output: "<b>aaabbb</b>"

Explanation:
"aa" appears as a substring two times: "aaabbb" and "aaabbb".
"b" appears as a substring three times: "aaabbb", "aaabbb", and "aaabbb".
Since the first two 's overlap, we merge them: "aaaabbb".
Since now the four 's are consecutive, we merge them: "aaabbb".