Question
Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.
For example,
Given [3,2,1,5,6,4] and k = 2, return 5.
Code
Version 1 (sort):
public class Solution {
public int findKthLargest(int[] nums, int k) {
Arrays.sort(nums);
return nums[nums.length - k];
}
}
Version 2 (heap):
public class Solution {
public int findKthLargest(int[] nums, int k) {
PriorityQueue<Integer> pq = new PriorityQueue<>(k);
for (int i = 0; i < k; i++) {
pq.offer(nums[i]);
}
for (int i = k; i < nums.length; i++) {
if (nums[i] > pq.peek()) {
pq.poll();
pq.offer(nums[i]);
}
}
return pq.peek();
}
}
Solution
方法一:直接排序,返回倒数第k个元素即可。
方法二:用小根堆。构建一个大小为k的小根堆,返回第一个元素即可。
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