# [LeetCode] 215. Kth Largest Element in an Array 数组中第k大的数字

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.

Example 1:

Input: [3,2,1,5,6,4] and k = 2
Output: 5


Example 2:

Input: [3,2,3,1,2,4,5,5,6] and k = 4
Output: 4

Note:
You may assume k is always valid, 1 ≤ k ≤ array's length.

class Solution {
public:
int findKthLargest(vector<int>& nums, int k) {
sort(nums.begin(), nums.end());
return nums[nums.size() - k];
}
};

class Solution {
public:
int findKthLargest(vector<int>& nums, int k) {
priority_queue<int> q(nums.begin(), nums.end());
for (int i = 0; i < k - 1; ++i) {
q.pop();
}
return q.top();
}
};

class Solution {
public:
int findKthLargest(vector<int>& nums, int k) {
int left = 0, right = nums.size() - 1;
while (true) {
int pos = partition(nums, left, right);
if (pos == k - 1) return nums[pos];
if (pos > k - 1) right = pos - 1;
else left = pos + 1;
}
}
int partition(vector<int>& nums, int left, int right) {
int pivot = nums[left], l = left + 1, r = right;
while (l <= r) {
if (nums[l] < pivot && nums[r] > pivot) {
swap(nums[l++], nums[r--]);
}
if (nums[l] >= pivot) ++l;
if (nums[r] <= pivot) --r;
}
swap(nums[left], nums[r]);
return r;
}
};

Github 同步地址：

https://github.com/grandyang/leetcode/issues/215

Wiggle Sort II

Top K Frequent Elements

Third Maximum Number

Kth Largest Element in a Stream

K Closest Points to Origin

https://leetcode.com/problems/kth-largest-element-in-an-array/

https://leetcode.com/problems/kth-largest-element-in-an-array/discuss/60294/Solution-explained

https://leetcode.com/problems/kth-largest-element-in-an-array/discuss/60309/C%2B%2B-PartitionMax-Heappriority_queuemultiset

LeetCode All in One 题目讲解汇总(持续更新中...)

 微信打赏 Venmo 打赏
posted @ 2015-05-30 04:10  Grandyang  阅读(29620)  评论(26编辑  收藏  举报