Solution: Substring with Concatenation of All Words
Explore an efficient sliding window approach to identify all starting indices where substrings concatenate all given words exactly once. Understand how to use frequency maps and stride-based iteration to optimize substring search without redundant checks.
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Statement
You are given a string, s, and an array of strings, words. All strings in words are of the same length.
A concatenated string is a string that contains all the words in words exactly once, in any order, concatenated together without any intervening characters.
Formally, a concatenated string is a permutation of all words joined together. For example, if words = ["ab", "cd", "ef"], then the following are all valid concatenated strings: "abcdef", "abefcd", "cdabef", "cdefab", "efabcd", "efcdab". However, "acdbef" is not valid because it is not formed by concatenating all the words in any order.
Your task is to return all starting indices of substrings in s that are concatenated strings.
You may return the indices in any order.
Constraints:
s.length...