#include <stdlib.h>

typedef struct {
    int key;
    int value;
    int used;
} Entry;

int hash(int key, int size) {
    return (key % size + size) % size;
}

int* twoSum(int* nums, int numsSize, int target, int* returnSize) {

    int tableSize = numsSize * 2;
    Entry* table = calloc(tableSize, sizeof(Entry));

    int* res = malloc(sizeof(int) * 2);
    *returnSize = 2;

    for (int i = 0; i < numsSize; i++) {
        int complement = target - nums[i];
        int h = hash(complement, tableSize);

        while (table[h].used) {
            if (table[h].key == complement) {
                res[0] = i;
                res[1] = table[h].value;
                free(table);
                return res;
            }
            h = (h + 1) % tableSize;
        }

        h = hash(nums[i], tableSize);
        while (table[h].used) {
            h = (h + 1) % tableSize;
        }

        table[h].used = 1;
        table[h].key = nums[i];
        table[h].value = i;
    }

    free(table);
    return res;
}