Wednesday, November 4, 2020

LeetCode [703] Kth Largest Element in a Stream

 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) 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.
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class KthLargest {
    PriorityQueue<Integer> pq = new PriorityQueue<>();
    int k;
    public KthLargest(int k, int[] nums) {
        this.k = k;
        for(int i : nums){
            pq.add(i);
            if(pq.size()>k) pq.poll();
        }
    }
    
    public int add(int val) {
        pq.add(val);
        if(pq.size()>k) pq.poll();
        return pq.peek();
    }
}

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