Problem: 215. 数组中的第K个最大元素

思路

👨‍🏫 参考

复杂度

时间复杂度: $O(n)$

空间复杂度: $O(\log n)$

Code

class Solution {public int findKthLargest(int[] nums, int k){List<Integer> list = new ArrayList<>();for (int x : nums)list.add(x);return quickSelect(list, k);}private int quickSelect(List<Integer> nums, int k){Random rand = new Random();int pivot = nums.get(rand.nextInt(nums.size()));List<Integer> big = new ArrayList<>();List<Integer> equal = new ArrayList<>();List<Integer> small = new ArrayList<>();for (int x : nums){if (x < pivot)small.add(x);else if (x == pivot)equal.add(x);elsebig.add(x);}if (k <= big.size())// 第 k 大在 big中return quickSelect(big, k);else if (big.size() + equal.size() < k)// 第 k 大在 small中return quickSelect(small, k - big.size() - equal.size());return pivot;// 当前选到的值就是第 k 大}
}