676
There are 676 possible 2-character strings.\n\nSo, we use a boolean array to track if we\'ve seen a string before.\n\n> Note that we track reversed strings in t
There are 676 possible 2-character strings.\n\nSo, we use a boolean array to track if we\'ve seen a string before.\n\n> Note that we track reversed strings in the boolean array.  \n\n**C++**\n```cpp\nint maximumNumberOfStringPairs(vector<string>& words) {\n    int vis[676] = {}, res = 0;\n    for (const auto &w : words) {\n        res += vis[(w[1] - \'a\') * 26 + w[0] - \'a\'];\n        vis[(w[0] - \'a\') * 26 + w[1] - \'a\'] = true;\n    }\n    return res;\n}\n```
['C']