703.Kth Largest Element in a Stream

tags: `Easy`,`Tree`,`Heap`

題目描述

Design a class to find the k^th largest element in a stream. Note that it is the k^th largest element in the sorted order, not the k^th 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 k^th largest element in the stream.

範例

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 k^th element.

解答

Python















class KthLargest:

    def __init__(self, k: int, nums: List[int]):
        self.k = k
        self.heap = []
        for num in nums:
            self.add(num)
        

    def add(self, val: int) -> int:
        if len(self.heap) < self.k:
            heapq.heappush(self.heap, val)
        elif val > self.heap[0]:
            heapq.heapreplace(self.heap, val)
        return self.heap[0]

Yen-Chi ChenTue, May 23, 2023
















class KthLargest:

    def __init__(self, k: int, nums: List[int]):
        self.k = k
        self.heap = nums
        heapq.heapify(self.heap)

        while len(self.heap) > self.k:
            heapq.heappop(self.heap)

    def add(self, val: int) -> int:
        heapq.heappush(self.heap, val)
        if len(self.heap) > self.k:
            heapq.heappop(self.heap)

        return self.heap[0]

Ron ChenTue, May 23, 2023

Javascript












class KthLargest {
  constructor(k, nums) {
    this.k = k;
    this.nums = nums;
  }

  add(val) {
    this.nums.push(val);
    this.nums.sort((a, b) => b - a);
    return this.nums[this.k - 1];
  }
}

用sort也會過ㄏㄏ
MarsgoatTue, May 23, 2023


















class KthLargest {
  constructor(k, nums) {
    this.k = k;
    this.minHeap = new MinHeap();
    for (const num of nums) {
      this.add(num);
    }
  }

  add(val) {
    this.minHeap.push(val);
    if (this.minHeap.size() > this.k) {
      this.minHeap.pop();
    }

    return this.minHeap.top();
  }
}

minHeap就不貼了，我直接讓chatGPT把我之前的maxHeap直接改寫成minHeap
MarsgoatTue, May 23, 2023

C++



















class KthLargest {
public:
    multiset<int> bst;
    int k;
    vector<int> nums;
    KthLargest(int k, vector<int>& nums) {
        this->k = k;
        for (int x : nums) {
            bst.insert(x);
        }
    }
    
    int add(int val) {
        bst.insert(val);
        auto it = bst.end();
        advance(it, -k);
        return *it;
    }
};

Jerry WuTrue, May23, 2023

Reference

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