Shortest Common Supersequence

Given two strings `str1` and `str2`, return the shortest string that has both `str1` and `str2` as subsequences. If multiple answers exist, you may return any of them. (A string S is a subsequence of string T if deleting some number of characters from T (possibly 0, and the characters are chosen anywhere from T) results in the string S.) Example 1: Input: str1 = "abac", str2 = "cab" Output: "cabac" Explanation: str1 = "abac" is a subsequence of "cabac" because we can delete the first "c". str2 = "cab" is a subsequence of "cabac" because we can delete the last "ac". The answer provided is the shortest such string that satisfies these properties. Note: `1 <= str1.length, str2.length <= 1000` `str1` and `str2` consist of lowercase English letters.