错误 C2109:下标需要数组或指针类型 5

我一直遇到一个关于for循环和数组的小问题，我希望我能得到一些帮助。在第一个函数中，使用 for 循环调用函数的每个值就可以了。但是，在第二个函数中，我从Visual Studio收到一个错误，指出"下标需要数组或指针类型"。我在这里做错了什么导致此错误？

该程序的目的是搜索书籍的txt文件，跳过条目之间的行，找出文件中有多少条目匹配以及它们的位置，并打印出每个条目的详细信息。

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 Numbern" << "2. Authorn" << "3. Titlen";
    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";
}