j from the stack, mark both i and j, and add i-j to the score.
Otherwise, push i onto the stack for this character.
Return the total score.
Code

[{"language":"C++","code":"class Solution {\npublic:\n    int mirrorScore(string s) {\n        unordered_map<char, char> mirror;\n        for (char c = 'a'; c <= 'z'; ++c) mirror[c] = 'z' - (c - 'a');\n        unordered_map<char, stack<int>> stks;\n        int ans = 0;\n        vector<bool> marked(s.size(), false);\n        for (int i = 0; i < s.size(); ++i) {\n            char m = mirror[s[i]];\n            if (!stks[m].empty()) {\n                int j = stks[m].top(); stks[m].pop();\n                ans += i - j;\n            } else {\n                stks[s[i]].push(i);\n            }\n        }\n        return ans;\n    }\n};","lang":"cpp","html":"<pre class=\"shiki shiki-themes github-light github-dark\" style=\"background-color:#fff;--shiki-dark-bg:#24292e;color:#24292e;--shiki-dark:#e1e4e8\" tabindex=\"0\"><code><span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">class</span><span style=\"color:#6F42C1;--shiki-dark:#B392F0\"> Solution</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> {</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">public:</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">    int</span><span style=\"color:#6F42C1;--shiki-dark:#B392F0\"> mirrorScore</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">(</span><span style=\"color:#6F42C1;--shiki-dark:#B392F0\">string</span><span style=\"color:#E36209;--shiki-dark:#FFAB70\"> s</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">) {</span></span>\n<span class=\"line\"><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">        unordered_map</span><span style=\"color:#D73A49;--shiki-dark:#F97583\">&#x3C;char</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\">, </span><span style=\"color:#D73A49;--shiki-dark:#F97583\">char></span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> mirror;</span></span>\n<span class=\"line\"><span style=\"color:#D73A49;--shiki-dark:#F97583\">        for</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> (</span><span style=\"color:#D73A49;--shiki-dark:#F97583\">char</span><span style=\"color:#24292E;--shiki-dark:#E1E4E8\"> c </span><span style=\"color:#D73A49;--shiki-dark:#F97583\">=</span><span style=\"color:#032F62;--shiki-dark:#9ECBFF\"> 'a'</span><span s
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