703

703. Kth Largest Element in a Stream (Easy)

Design a class to find the kth largest element in a stream. Note that it is the kth largest element in the sorted order, not the kth distinct element.

Implement KthLargest class:

• KthLargest(int k, int[] nums) Initializes the object with the integer k and the stream of integers nums.
• int add(int val) Appends the integer val to the stream and returns the element representing the kth largest element in the stream.

 

Example 1:

Input
["KthLargest", "add", "add", "add", "add", "add"]
[[3, [4, 5, 8, 2]], [3], [5], [10], [9], [4]]
Output
[null, 4, 5, 5, 8, 8]

Explanation
KthLargest kthLargest = new KthLargest(3, [4, 5, 8, 2]);
kthLargest.add(3);   // return 4
kthLargest.add(5);   // return 5
kthLargest.add(10);  // return 5
kthLargest.add(9);   // return 8
kthLargest.add(4);   // return 8

 

Constraints:

• 1 <= k <= 104
• 0 <= nums.length <= 104
• -104 <= nums[i] <= 104
• -104 <= val <= 104
• At most 104 calls will be made to add.
• It is guaranteed that there will be at least k elements in the array when you search for the kth element.

Companies:
Amazon, Facebook

Related Topics:
Tree, Design, Binary Search Tree, Heap (Priority Queue), Binary Tree, Data Stream

Similar Questions:

• Kth Largest Element in an Array (Medium)
• Finding MK Average (Hard)
• Sequentially Ordinal Rank Tracker (Hard)

Solution 1. Heap

// OJ: https://leetcode.com/problems/kth-largest-element-in-a-stream/
// Author: github.com/lzl124631x
// Time:
//     KthLargest: O(NlogK)
//     add: O(logK)
// Space: O(N)
class KthLargest {
private:
    priority_queue<int, vector<int>, greater<>> pq;
    int k;
public:
    KthLargest(int k, vector<int> A): k(k) {
        for (int n : A) {
            pq.push(n);
            if (pq.size() > k) pq.pop();
        }
    }
    int add(int val) {
        pq.push(val);
        if (pq.size() > k) pq.pop();
        return pq.top();
    }
};