// SQL solution concept with C
#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>
#include <string.h>

static const char* getExpensiveCitiesQuery() {
    return "SELECT city "
           "FROM Listings "
           "GROUP BY city "
           "HAVING AVG(price) > ("
           "    SELECT AVG(price) "
           "    FROM Listings"
           ") "
           "ORDER BY city ASC";
}

typedef struct {
    char cities[100][50];
    int count;
} CityResult;

static int callback(void *data, int argc, char **argv, char **azColName) {
    CityResult *result = (CityResult*)data;
    if (argc > 0 && argv[0]) {
        strcpy(result->cities[result->count], argv[0]);
        result->count++;
    }
    return 0;
}

CityResult findExpensiveCities(sqlite3 *db) {
    CityResult result = {0};
    char *errMsg = 0;
    
    // Create and populate sample data first
    sqlite3_exec(db, 
        "CREATE TABLE IF NOT EXISTS Listings ("
        "listing_id INTEGER, city TEXT, price INTEGER)", 
        0, 0, &errMsg);
    
    // Insert sample data (simplified)
    sqlite3_exec(db,
        "INSERT INTO Listings VALUES "
        "(1, 'New York', 500000),"
        "(2, 'New York', 600000),"
        "(3, 'Chicago', 300000),"
        "(4, 'Chicago', 350000),"
        "(5, 'San Francisco', 800000),"
        "(6, 'San Francisco', 900000),"
        "(7, 'Dallas', 200000),"
        "(8, 'Dallas', 250000)",
        0, 0, &errMsg);
    
    // Execute main query
    sqlite3_exec(db, getExpensiveCitiesQuery(), callback, &result, &errMsg);
    
    return result;
}