Longest Chain of Single-Letter Insertions

### Problem Choose a chain of words from `words`. Each next word must result from inserting exactly one letter into the preceding word without changing the order of existing letters. A lone word is a chain of length 1. Return the greatest chain length. ```cpp class Solution { public: int longestStrChain(vector<string>& words); }; ``` ### Examples **Example 1:** ```text Input: words = ["a","ac","bac","bacc","zz"] Output: 4 Explanation: a -> ac -> bac -> bacc adds one letter at each step. ``` **Example 2:** ```text Input: words = ["ab","ba","xyz"] Output: 1 Explanation: Equal-length words cannot be consecutive in a chain, and deleting one character from xyz yields neither ab nor ba. ``` ### Constraints - There are 1 to 1000 input words. - Each word has length 1 to 16. - Words use lowercase English letters only. ### Contract considerations Use only words from the given list. Return the chain length, not one selected chain. ```hint Read the boundary condition Must every word in a proposed chain occur in the input, and can equal-length words form a step? ``` ### Boundary reminders Use only words from the given list. Return the chain length, not one selected chain.