Give me the most optimised c++ code with passing a...

This is O(|S|) time and handles duplicates, hyphens, case conversion, and 8-character last-name truncation.

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

string solution(string &S, string &C) {
    unordered_map<string, int> cnt;
    string ans;

    transform(C.begin(), C.end(), C.begin(), ::tolower);

    size_t pos = 0;
    while (pos < S.size()) {
        size_t end = S.find("; ", pos);
        string name = S.substr(pos, end == string::npos ? string::npos : end - pos);

        string first = name.substr(0, name.find(' '));
        string last = name.substr(name.rfind(' ') + 1);

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

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

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

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

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

        if (end == string::npos) break;
        pos = end + 2;
    }

    return ans;
}

For the screenshot example, it correctly produces [email protected], then [email protected], [email protected], and watson-parker becomes watsonpa after removing the hyphen before truncating.

The errors in the screenshot are from a few typing mistakes like size_tpos instead of size_t pos, '' instead of ' ', and misspelled string::npos.

Copy this exact code:

cpp
#include <string>
#include <unordered_map>
#include <algorithm>
#include <cctype>

using namespace std;

string solution(string &S, string &C) {
    unordered_map<string, int> count;
    string result;

    string company = C;
    transform(company.begin(), company.end(), company.begin(),
              [](unsigned char c) { return tolower(c); });

    size_t pos = 0;

    while (pos < S.size()) {
        size_t end = S.find("; ", pos);

        string name = S.substr(
            pos,
            end == string::npos ? string::npos : end - pos
        );

        string first = name.substr(0, name.find(' '));
        string last = name.substr(name.rfind(' ') + 1);

        last.erase(remove(last.begin(), last.end(), '-'), last.end());

        if (last.size() > 8)
            last.resize(8);

        transform(first.begin(), first.end(), first.begin(),
                  [](unsigned char c) { return tolower(c); });

        transform(last.begin(), last.end(), last.begin(),
                  [](unsigned char c) { return tolower(c); });

        string base = first + "." + last;

        int n = ++count[base];

        string email = base;
        if (n > 1)
            email += to_string(n);

        email += "@" + company + ".com";

        if (!result.empty())
            result += "; ";

        result += name + " <" + email + ">";

        if (end == string::npos)
            break;

        pos = end + 2;
    }

    return result;
}

Important

Make sure these characters are typed exactly:

cpp
name.find(' ')
name.rfind(' ')
string::npos
size_t pos = 0;
size_t end = S.find("; ", pos);

For the example, it correctly generates:

text
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]

Complexity is O(N), where N is the length of the input string.