[Leetcode] Palindrome Pairs palindrome on

Given a list of unique words. Find all pairs of distinct indices (i, j) in the given list, so, the concatenation of the-words, i.e. is a palindrome.

Example 1:
Given words =["bat", "tab", "cat"]
Return[[0, 1], [1, 0]]
The palindromes is["battab", "tabbat"]

Example 2:
Given words =["abcd", "dcba", "lls", "s", "sssll"]
Return[[0, 1], [1, 0], [3, 2], [2, 4]]
The palindromes is["dcbaabcd", "abcddcba", "slls", "llssssll"]

Credits:
Special thanks to @dietpepsi for adding this problem and creating all test cases.

[Leetcode] Palindrome Pairs palindrome on