// 2053. Kth Distinct String in an Array #include "leetcode.h" /* * a distinct string is a string that is present only once in an array. given an * array of strings 'arr' and an integer 'k', return the k'th eldistinct string * present in 'arr'. if there are fewer than 'k' distinct strings, return an * empty string "". note the strings are considered in the order in which they * appear in the array. */ typedef struct { char str[6]; bool distinct; int pos; UT_hash_handle hh; } element; int cmp_pos(const element *e1, const element *e2) { return e1->pos - e2->pos; } char *kthDistinct(char **arr, int arrSize, int k) { element *hash = NULL, *e; for (size_t i = 0; i < arrSize; i++) { const char *str = arr[i]; HASH_FIND_STR(hash, str, e); if (e) { e->distinct = false; } else { e = (element *)malloc(sizeof(*e)); e->distinct = true; e->pos = i; strcpy(e->str, str); HASH_ADD_STR(hash, str, e); } } HASH_SORT(hash, cmp_pos); char *ans = (char *)malloc(6 * sizeof(char)); *ans = '\0'; int i = 0; for (e = hash; e; e = e->hh.next) if (e->distinct) if (++i == k) { strcpy(ans, e->str); break; } return ans; } int main() { char *a1[] = {"d", "b", "c", "b", "c", "a"}, *a2[] = {"aaa", "aa", "a"}, *a3[] = {"a", "b", "a"}; printf("%s\n", kthDistinct((char **)a1, ARRAY_SIZE(a1), 2)); // expect: a printf("%s\n", kthDistinct((char **)a2, ARRAY_SIZE(a2), 1)); // expect: aaa printf("%s\n", kthDistinct((char **)a3, ARRAY_SIZE(a3), 3)); // expect: null }