Minimum Substring to Cover All Words

You are given a list of words and a longer string `s`. Your task is to find the minimum length substring from `s` that contains all the words from the list at least once. If such a substring does not exist, return '' (an empty string). Input Format: The input consists of two lines. The first line contains an integer `n`, the number of words in the list. The second line contains `n` space-separated words, followed by the string `s` on the same line (after a space). Output Format: Output the minimum substring containing all the words, or '' if it does not exist. Example: Input: 4 this is a test a string this is a test string for our function Output: 'this is a test a string'