Concatenate words in such a way as to obtain the longest possible sub-string of the same letter
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An array of N words is given. Each word consists of small letters ('a'- 'z'). Our goal is to concatenate the words in such a way as to obtain a single word with the longest possible sub-string composed of one particular letter. Find the length of such a sub-string. Examples: Given N=3 and words=['aabb','aaaa','bbab'], your function should return 6. One of the best concatenations is words[1]+words[0]+words[2]='aaaaaabbbbab'. The longest sub-string is composed of the letter 'a' and its length is 6. Given N=3 and words=['xxbxx','xbx','x'], your function should return 4. One of the best concatenations is words[0]+words[2]+words[1]='xxbxxxxbx'. The longest sub-string is composed of letter 'x