So I have wrote a program that uses auto however the compiler doesn't seem to recognize it, probably it is an earlier compiler.

I was wondering for my code, with are suitable variables to fix my code so that I do not need to use the auto keyword? I'm thinking a pointer to a string? or a string iterator, though I am not sure.

  #include <cstdlib>
    #include <string>
    #include <iostream>
    #include <unistd.h>
    #include <algorithm>
    using namespace std;

    int main(int argc, char* argv[]) {

        enum MODE {
            WHOLE, PREFIX, SUFFIX, ANYWHERE, EMBEDDED
        } mode = WHOLE;
        bool reverse_match = false;

        int c;
        while ((c = getopt(argc, argv, ":wpsaev")) != -1) {
            switch (c) {
                case 'w': // pattern matches whole word
                    mode = WHOLE;
                    break;
                case 'p': // pattern matches prefix
                    mode = PREFIX;
                    break;
                case 'a': // pattern matches anywhere
                    mode = ANYWHERE;
                    break;
                case 's': // pattern matches suffix
                    mode = SUFFIX;
                    break;
                case 'e': // pattern matches anywhere
                    mode = EMBEDDED;
                    break;
                case 'v': // reverse sense of match
                    reverse_match = true;
                    break;
            }
        }
        argc -= optind;
        argv += optind;

        string pattern = argv[0];


        string word;
        int matches = 0;

        while (cin >> word) {

            switch (mode) {
                case WHOLE:
                    if (reverse_match) {
                        if (pattern != word) {
                            matches += 1;
                            cout << word << endl;
                        }
                    } else if (pattern == word) {
                        matches += 1;
                        cout << word << endl;
                    }
                    break;
                case PREFIX:
                    if (pattern.size() <= word.size()) {
                        auto res = mismatch(pattern.begin(), pattern.end(), word.begin());

                        if (reverse_match) {
                            if (res.first != word.end()) {
                                matches += 1;
                                cout << word << endl;
                            }
                        } else if (res.first == word.end()) {
                            matches += 1;
                            cout << word << endl;
                        }
                    }
                    break;
                case ANYWHERE:

                    if (reverse_match) {
                        if (!word.find(pattern) != string::npos) {
                            matches += 1;
                            cout << word << endl;
                        }
                    } else if (word.find(pattern) != string::npos) {
                        matches += 1;
                        cout << word << endl;
                    }
                    break;
                case SUFFIX:
                    if (pattern.size() <= word.size()) {
                        auto res = mismatch(pattern.rbegin(), pattern.rend(), word.rbegin());

                        if (reverse_match) {
                            if (res.first != word.rend()) {
                                matches = +1;
                                cout << word << endl;
                            }
                        } else if (res.first == word.rend()) {
                            matches = +1;
                            cout << word << endl;
                        }
                    }
                    break;
                case EMBEDDED:
                    if (reverse_match) {
                        if (!pattern.find(word) != string::npos) {
                            matches += 1;
                            cout << word << endl;}

                    } else if (pattern.find(word) != string::npos) {
                        matches += 1;
                        cout 

<< word << endl;
                }
                break;
        }

    }
    return (matches == 0) ? 1 : 0;
}

Thanks in advance!