Optimal approach: Identify the best algorithm base...

Question

Optimal approach: Identify the best algorithm based on the problem constraints. Avoid brute force if a more efficient solution exists.
Simple logic: Use the simplest approach that achieves optimal or best practical complexity.
Concise code: Write short, clean, readable C++ code without unnecessary variables, functions, comments, or explanations.
C++ standard: Use C++17 and STL efficiently.
Time complexity: Minimize execution time and analyze the worst-case complexity.
Space complexity: Minimize auxiliary memory usage without sacrificing correctness or performance.
Edge cases: Handle empty inputs where applicable, duplicates, negative values, boundary conditions, and integer overflow

Answer 1

Use one pass through the names and an unordered_map to count duplicate base email addresses.

cpp
#include <string>
#include <sstream>
#include <unordered_map>
#include <algorithm>
#include <vector>
using namespace std;

string solution(string &S, string &C) {
    transform(C.begin(), C.end(), C.begin(), ::tolower);

    unordered_map<string, int> cnt;
    stringstream ss(S);
    string name, ans;

    while (getline(ss, name, ';')) {
        if (!name.empty() && name[0] == ' ')
            name.erase(0, 1);

        stringstream ns(name);
        vector<string> parts;
        string x;
        while (ns >> x) parts.push_back(x);

        string first = parts.front();
        string last = parts.back();

        transform(first.begin(), first.end(), first.begin(), ::tolower);
        transform(last.begin(), last.end(), last.begin(), ::tolower);

        last.erase(remove(last.begin(), last.end(), '-'), last.end());
        if (last.size() > 8) last.resize(8);

        string base = first + "." + last;
        int n = ++cnt[base];

        string email = base;
        if (n > 1) email += to_string(n);
        email += "@" + C + ".com";

        if (!ans.empty()) ans += "; ";
        ans += name + " <" + email + ">";
    }

    return ans;
}

Complexity:

Time: O(|S| + |C|) expected
Auxiliary space: O(N) for duplicate-email counts, where N is the number of employees.

It correctly handles middle names, case conversion, hyphen removal before the 8-character truncation, and duplicate addresses such as john.doe2@..., john.doe3@....

Optimal approach: Identify the best algorithm base...

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