#include <stdlib.h>
#include <stdio.h>

// Someone complained that it was unreasonable to expect them to
// implement a hash table in C on a whiteboard in 30 minutes, so I
// wrote this in 15 minutes.
// https://news.ycombinator.com/item?id=26595520

enum { table_size = 1024 };
typedef struct item { int k, v, full; } item;
static item table[table_size];

void put(item kv)
{
    // dumbest possible hash function
    size_t orig = (size_t)kv.k % table_size;
    size_t b = (orig + 1) % table_size;
    // use linear probing for collisions
    while (table[b].full && table[b].k != kv.k && b != orig) {
      b = (b + 1) % table_size;
    }
    if (b == orig) abort();  // table full
    table[b] = kv;
    table[b].full = 1;
}

item *get(int k)
{
    size_t orig = (size_t)k % table_size;
    size_t b = (orig + 1) % table_size;
    while (table[b].full && table[b].k != k && b != orig) {
        b = (b + 1) % table_size;
    }
    return (table[b].full && table[b].k == k) ? &table[b] : NULL;
}

int main()
{
  put((item) { 4, 7 });
  put((item) { 1028, 9 });
  put((item) { 3, 25 });
  printf("%d %d %d %p %p\n", get(4)->v, get(1028)->v, get(3)->v, get(5), get(3));
  put((item) { 4, 8 });
  printf("%d %d %d %p %p\n", get(4)->v, get(1028)->v, get(3)->v, get(5), get(3));
  put((item) { -10280000, 90 });
  return 0;
}