Given an array of string words. Return all strings in words which is substring of another word in any order. String words[i] is substring of words[j], if can be obtained removing some characters to left and/or right side of words[j]. Example 1: Input: words = ["mass","as","hero","superhero"] Output: ["as","hero"] Explanation: "as" is substring of "mass" and "hero" is substring of "superhero". ["hero","as"] is also a valid answer. Example 2: Input: words = ["leetcode","et","code"] Output: ["et","code"] Explanation: "et", "code" are substring of "leetcode". Example 3: Input: words = ["blue","green","bu"] Output: [] Constraints: 1 <= words.length <= 100 1 <= words[i].length <= 30 words[i] contains only lowercase English letters. It's guaranteed that words[i] will be unique.