Arrays 通过函数修改结构数组的单个元素

我有一段代码，用来记录城市的名字和他们在一系列结构中的总的新冠病毒病例。内存分配必须动态完成，最初有3个空空间。用户输入3个城市后，将为下一次添加分配更多内存。但是，每当我添加一个城市和案例总数时，我都无法访问它们。我得到随机目录、字符或随机数。我认为我使用指针的方式有问题。我到底做错了什么

    #include <stdio.h>
    #include <stdlib.h>
    #define  MAX_CHAR 50
    
    typedef struct covid_cities{
        char name[MAX_CHAR];
        int cases;
        int ID;
    }COVID;

void addCity(COVID *cities, int number_of_cities){
    if (number_of_cities<3){
        cities[number_of_cities].ID=number_of_cities;
        printf("Enter the name of the city: ");
        scanf("%s", cities[number_of_cities].name);
        printf("Enter the total covid cases: ");
        scanf("%d", &cities[number_of_cities].cases);
        printf("%s is added!\n", cities[number_of_cities].name);
    }

    else{
        cities = (COVID *)realloc(cities, (number_of_cities+2)*sizeof(COVID));
        cities[number_of_cities].ID=number_of_cities;
        printf("Enter the name of the city: ");
        scanf("%s", cities[number_of_cities].name);
        printf("Enter the total covid cases: ");
        scanf("%d", &cities[number_of_cities].cases);
        printf("%s is added!\n", cities[number_of_cities].name);
    }
}
int main(void){
    int number_of_cities = 0;
    while(1){
        int user_input;
        COVID *cities;
        cities = (COVID *)malloc(sizeof(COVID)*3);
        printf("Covid Cases By City\n");
        printf("1) Add city\n");
        printf("What would you like to do? ");
        scanf("%d", &user_input);
        switch(user_input){
            case 1:
                addCity(cities, number_of_cities);
                number_of_cities++;
                break;
           default:
                printf("Invalid Input\n");
        }
    }
}

#包括
#包括
#定义最大字符50
类型定义结构新冠城市{
字符名称[最大字符]；
int案例；
int-ID；
}新冠病毒；
void addCity（新冠病毒*城市，城市的整数）{
如果（城市数量）移动
COVID*cities；cities=（COVID*）malloc（sizeof（COVID）*3）；
在
while
循环之外。想到这件事这么简单……我真傻！非常感谢你。