main.c

// one pass hash table solution with uthash

typedefstruct {
intvalue;
intindex;
UT_hash_handlehh;
} hashTable;

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int*twoSum(int*nums, intnumsSize, inttarget, int*returnSize){
if(nums==NULL||numsSize==0) {
*returnSize=0;
returnNULL;
 }
*returnSize=2;
int*result= (int*)malloc(*returnSize*sizeof(int));

hashTable*hash=NULL, *elem, *temp;

for(inti=0; i<numsSize; i++) {
intlookupKey=nums[i];
intcomplement=target-lookupKey;
HASH_FIND_INT(hash, &complement, elem);
if(elem) {
result[0] =elem->index;
result[1] =i;
break;
 }

elem=malloc(sizeof(hashTable));
elem->value=nums[i];
elem->index=i;
HASH_ADD_INT(hash, value, elem);
 }

HASH_ITER(hh, hash, elem, temp) {
free(elem);
 }

returnresult;
}