LeetCode in Erlang
215. Kth Largest Element in an Array
Medium
Given an integer array nums and an integer k, return the kth largest element in the array.
Note that it is the kth largest element in the sorted order, not the kth distinct element.
You must solve it in O(n) time complexity.
Example 1:
Input: nums = [3,2,1,5,6,4], k = 2
Output: 5
Example 2:
Input: nums = [3,2,3,1,2,4,5,5,6], k = 4
Output: 4
Constraints:
1 <= k <= nums.length <= 105-104 <= nums[i] <= 104
Solution
-spec find_kth_largest(Nums :: [integer()], K :: integer()) -> integer().
find_kth_largest(Nums, K) ->
Q = gb_sets:new(),
FinalQ = lists:foldl(fun({N, I}, AccQ) ->
case gb_sets:is_element({N, I}, AccQ) of
true -> AccQ;
false ->
case gb_sets:size(AccQ) < K of
true ->
gb_sets:insert({N, I}, AccQ);
false ->
{Smallest, TempQ} = gb_sets:take_smallest(AccQ),
gb_sets:insert(max(Smallest, {N, I}), TempQ)
end
end
end, Q, lists:zip(Nums, lists:seq(1, length(Nums)))),
element(1, gb_sets:smallest(FinalQ)).
% Helper function to find the maximum of two tuples based on their first element.
max({N1, I1}, {N2, I2}) when N1 >= N2 -> {N1, I1};
max(_, {N2, I2}) -> {N2, I2}.