问错误c2109:下标要求数组或指针类型为5

EN

void bookSearch(string id) {
    ifstream fbooks;

    string item = " ", entry = " ";

    int resultLocation[30];

    int searchType = 0;

    fbooks.open("books.txt");

    cout << "Welcome to the Book Search System, " << id << ".\n"
        << "What do you wish to search the registry by?\n"
        << "1. ISBN Number\n" << "2. Author\n" << "3. Title\n";

    while (searchType<1 || searchType>3) {
        cin >> searchType;

        if (searchType<1 || searchType>3) {
            displayMessage(0);

        }
    }

    getline(cin, item);

    for (int x = 0; x <= 30; x++) {
        for (int y = 0; y < searchType; y++)
            getline(fbooks, entry);

        if (entry == item)
            resultLocation[x] = 1;
        else
            resultLocation[x] = 0;

        for (int z = 0; z < 5; z++)
            getline(fbooks, entry);
    }

    resultPrint(resultLocation, id);
}


void resultPrint(int resultLocation, string id){
    int resultNum = 0;

    string entry = "";

    ifstream fbooks;

    fbooks.open("books.txt");

    for (int a = 0; a <= 30; a++) {
        if (resultLocation == 1)
            resultNum++;
    }

    if (resultNum > 0) {
        cout << endl << "There are " << resultNum << " entries in the database matching that criteria.\n";

        for (int a = 0; a <= 30; a++){
            if (resultLocation[a] == 1) { //The a in this line is marked with the error
                for (int b = 0; b <= 2; b++) {
                    getline(fbooks, entry);
                    cout << entry;
                }
            }
        }
    }

    else
        cout << endl << "There are no entries in the database matching that criteria.\n";
}