sem10_2

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define HASH_SIZE 512

struct city
{
 char* name;
 unsigned population;
};
typedef struct city* city_pointer;
typedef struct table_elem* table_pointer;
struct table_elem
{
 city_pointer city;
 table_pointer next;
};
int get_option();
unsigned hash(char* name);
void add_city(char* name, unsigned population);
void print_cities();
void remove_city(char* name);
table_pointer table[HASH_SIZE];

int main()
{
  for(int i = 0; i != HASH_SIZE; ++i)
   table[i] = NULL;
  for(;;)
  {
   switch(get_option())
   {
    case 1:
    {
        printf("Input city name:");
        char name[128];
        scanf("%s", name);
        printf("Input city population:");
        int ppl;
        scanf("%d", &ppl);
        add_city(name, ppl);
    }
    break;
    case 2:
   {
       printf("Input city name:");
       char name[128];
       scanf("%s", name);
       remove_city(name);
   }
    break;
    case 3:
     print_cities();
    break;
   };
  }
}
int get_option()
{
 puts("1. Add city");
 puts("2. Remove city");
 puts("3. List cities");
 int option;
 scanf("%d", &option);
 return option;
}
unsigned hash(char* name)
{
 unsigned result = 0;
 for(;*name != '\0'; ++name)
 {
  result = *name + result * 31;
 }
 return result % HASH_SIZE;
}
void add_city(char* name, unsigned population)
{
 unsigned h = hash(name);
 table_pointer curr = table[h];
 if(table[h] == NULL)
 {
    table[h] = (table_pointer)malloc(sizeof(struct table_elem));
    curr = table[h];
 }
 else
 {
     while(curr->next != NULL)
      curr = curr->next;
     curr = (table_pointer)malloc(sizeof(struct table_elem));
 }
 curr->city = (city_pointer)malloc(sizeof(struct city));
 curr->city->name = (char*)malloc(strlen(name));
 strcpy(curr->city->name, name);
 curr->city->population = population;
 curr->next = NULL;
}
void print_cities()
{
 for(int i = 0; i != HASH_SIZE; ++i)
 {
  table_pointer curr = table[i];
  while(curr != NULL)
  {
   printf("%s -- Population: %d\n", curr->city->name, curr->city->population);
   curr = curr->next;
  }
 }
}
void remove_city(char* name)
{
    unsigned h = hash(name);
    table_pointer prev = NULL;
    table_pointer curr = table[h];
    if(curr == NULL)
    {
        puts("This city does not exist!!");
        return;
    }
    do
    {
        //printf("|%s|%s|", curr->city->name, name);
        if(!strcmp(curr->city->name, name))
        {
            if(prev == NULL)
            {
                table[h] = curr->next;
            }
            else
            {
                prev->next = curr->next;
            }
            free(curr->city->name);
            free(curr->city);
            puts("This city is successfully removed!");
            return;
        }
        prev = curr;
        curr = curr->next;
    }while(curr->next != NULL);
    puts("This city does not exist!");
    return;
}